Lordyboi

Since yours is Manifold and tune, its not complicated but you can get it tuned many ways. One way is like Martin has suggested. Another approach is:
1. 95 Octane / Standard fuel tune , Standard throttle 
2. 97 Octane tune , Standard Throttle
3. 99 Octane tune, Sensitive Throttle
4. 99 Octane tune with Racerom features (Auto Blip, Launch Control, Flat Foot Shift) and Sensitive throttle
 
Or you can choose permutations and combinations of by mixing and matching.

No, the dongle isn't needed and I have my Scangauge gauges plugged into the OBD2 port.
You can ask for different programmes for the four modes, too.  I have these:
1. Full power
2. Full power plus auto-blip
3. Lower power for standard fuel
4. Shutdown (will not start)

You can read about the features here. The software allows these options, does Flat foot shift give you any real gain especially in an NA car is a good question and probably limited gains , if you do a lot of track time then the time to depress and release clutch is saved.. which will be milli seconds. Thats about it.
 
https://www.ecutek.com/what-are-racerom-special-features/
 

No you don't have anything with ecutek. You just pay the license and get the car tuned. All by Abbey, you come in with your car and leave with your car with no 'physical' additions to the car

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You don't need to leave it in the OBD2 port. I have the ECuTek dongle permanently in because I use it to monitor the car, but the car runs fine without it attached.

No need for usage video though, there are already several EJECTO SEATO CUZ on youtube guides

Yes, I have the eject decal already. Haven't yet told my partner about it...

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It's a little hard to explain, I discovered what was buzzing after searching "gt86 door rattle and watching the video I linked, go to 1:40 they show what I mean. In the video they somehow remove it from the plastic piece that screws into the door card. I was too scare of breaking the clips when I tried to remove it so just wrapped mine in a load of electrical tape which seem to have done the trick for now but I think I'm just going to glue it in place when I next have the door cards off but its up to you what you choice to do.
The tolerance in the two plastic pieces is shocking and when the volume of the speakers is even moderately loud the control box vibrates like mad making an irritating buzzing sound. Make sure you do the window controls on both door cards as they both vibrate.  
I'll try and explain better if this still isn't enough

I'm currently in the process of doing this my self, currently only have some CCF and a little sound deadening mat. Nothing rattles now but road noise is unbearable, so im going to put in MLV in under the carpet and door cards in the summer when its warmer.
Here are some good links I've been using, might as well save you the time:
https://www.ft86club.com/forums/showthread.php?t=53511
https://www.flickr.com/photos/86194869@N08/sets/72157633425405068/with/8711031372/
https://www.ft86club.com/forums/showthread.php?t=35604
materials:
https://uk.rs-online.com/web/p/acoustic-insulation/8814557/
https://www.carinsulation.co.uk/product/car-heavy-layer-insulation-3mm-5kg-car-heavy-layer-deadening-5m-roll
https://www.amazon.co.uk/Yaheetech-Proofing-Deadening-Insulation-Adhesive/dp/B01MDUB6T6/ref=sr_1_7?crid=1PRW4Y2I9IIF8&dchild=1&keywords=closed+cell+foam&qid=1610298378&sprefix=closed+cel%2Caps%2C170&sr=8-7
These aren't the cheapest materials so do look around but they'll give you a feel.
In sort different materials block different wave length of sound (vibrations, road noise, wind noise all have different wave lengths) there is no one material fits all unfortunately. The forums I linked above do a good job of explaining what materials should be used where.
Do note that they will add weight, MLV will add the most mass by a mile but it the best a blocking road noise and worth it to stop my ears from bleeding.
Also I have the focal speaker package, Kenwood head unit as well as some better 3 1/2 inch speakers in the rear, great sound and more powerful but they cause my door cards to vibrate and rattle when a song with bass comes on. So the door cards they're coming off in the summer to address this. Just food for thought.
Finally when you have the door cards off tape/glue/wedge something in between the housing of the window controls and housing they sit in. You'll thanks me later.
Hope this all helps 

I bought a £25 item and paid £25 for shipping then paid another £25 for import duty so it’s karma for that scam😂
(the MTEC clutch spring)
oh and thanks for the re assurance !

If you plug straight in I think you get what you are after generally to get the v to light up with side lights alterations are needed but no photos as mine is wired up for three functions 
 

Yeh typically they send you a letter when they have your item on UK soil and then you have 3 weeks or so to pay import and then they'll ship it from your local depot to your door. Alternatively if you see your package is at your local depot on their tracking app before you receive the letter you can pop in and see if they'll give it to you early.
This is what I did, I was driving by my local parcel force depot and went in and asked and they were happy to give it to me but now thinking about it this could be why I didn't get away with import as they probably looked a little closer at my parcel as I was asking for it from the front desk apposed to a robot/computer sorting it and missing the import charge, but that just a guess. 
No if you've got your parcel and they sent it directly to you with out sending you a letter saying you need to pay import then that's fine, if you don't pay import they don't fine you they just send your parcel back to where it came from.
Has happened to me as well when I ordered something that cost £30 I paid no import. Again im just guessing here but if they have a high volume of parcels they might not be able to check them all ect. 

Just checked, they put £109 for me also but according to .GOV website you've got to pay tax on anything over £15 so I guess yours slipped trough the crack. lucky!