This is a brief summary i have put together after 15 mins of doing searches. Hope its useful to all other mk4 owners and prospective owners.. Rear beam bushes, they fail regularly at relativley low miles replace with new ones. Funny noise on start up. air con/climate,or starter motor usually Dump Valve, dont get one! Will force you car in to limp mode and make you look like a chav. Bigger brakes on a buget.if you have 280s use 312s carriers from later mk4 turbos and your existing calipers. Lowering you can only get away with 30mm drop before you have to start looking at a new arb, and possibly even adjustable drop links if your going very low. The badging doesnt mean anything really most of the time it was left to the dealers who propmtly forgot to do anything so cars are mis badged all the time. Poor running can be attrubuted to many things but MAF are also a common weakness with the mk4s. turbo flatspot (prob dodgy MAF), maybe dodgy coilpacks too. MAP sensors have been known to go also causing bad running misfires etc. How far can i go on std internals? The common concensus is about 300bhp before engine components start failing. Also keep an eye out for dodgy window operation, DV(diverter valve) failure n75 valve also cause limp mode Broken rear washer jet leading to tailgate lock/switch failure Headlight / side light bulbs are a mare to change. water pump (crappie plastic type) have a bad rep.