6 speed would require many more parts also, new clutch, flywheel, starter motor, driveshafts, salve cylinder, hydraulic lines, all sorts.
I'd suggest that getting a mk4 from 150-300bhp is likely to cost you a lot more than £2000 to do it properly.
The diff install alone will be around £1000+, then the same again for forged rods if you actually expect it to last any time at all. Another £1k on the turbo, actuator, turbo intake pipe to suit, and required manifold porting. And you're at £3k already before you've bought a downpipe, cat back exhaust system, MAF, injectors, FMIC, or most importantly a decent custom map! Not to mention a decent clutch and flywheel required to hold it all together.
I'm nto saying for one minute don't do it, a 300bhp mk4 is great fun, especially if it handles well already. Just be aware of teh true costs to get to where you want to be. at £200 per month it'll take you almost 2 years saving to do it all!
