Goth runs 280's on his and i havnt heard him say anything about fading maybe you could ask him what he is running cant remember if its red or yellow stuff pads with grooved discs
doesnt even have to be the same size as you can get 4" ones made but these ar more for charged cars i would think the actual limit is done by the wiring keep the standard maf and extend the wiring
dont know how long polys will last took 4 hours to get the axle off remove old bushes and refit, polys just slide in but are a pain to get back into the axle supports as they are wider and stiffer not to noticable on standard suspension
the wheels will fit depends on tyre sizes as to wether or not the speedo reads true as above TYREBIBLE is a good read "page 2" i have audi tt 6 spoke alloys with 195/40/17 for looks but they arnt the most comfortable 205/40/17 are better but arches may be a problem on lowered cars
It is possible take it to a decent garage and get them to do a sniff test (checks for combustion in water if oil is not showing or fudge not present in oil system)
If its not fitted they cant test it could just get some doublesided sticky tape and remove clean and restick yours. I like the third brake light mine didnt have one so i bought a spoiler with one in