Future owner,few questions :)

[iNs0mN1a]

I'm moving to U.K so that means my dream car will be alot cheaper ,then finding a LHD one...
I'm going to buy a (stock) TT Supra,manual transmission of course and make a little rocket from it but i have a few questions:
1)At what maximum mileage should i look so i could have the car at least 2-3 years and use it quite frequently without any major problems?150k km?
2)What's the maximum hp i could achieve on normal fuel(without having to mix it with meth..etc).Or if i run on meth(or smth else?) what does that involve(fuel system,fuel consumption,fuel cost,mixing ?? etc)i'm quite a noob at fuel beside the normal one.
3)How many hp's will a BPU++ supra have and how many will a APU(+) have?
4)What are the best quality / price parts i should look for?(exhaust(full),bov,greedy bcc?etc...)
Thank you very much!
Pwpanas you're help would be godlike!