Brother has the 100bhp TDI & he said earlier he was thinking an engine transplant may be cheaper than buying a new car outright.
I don't think he's too keen on anything that sups a lot of juice (so R32 engine & the like would be out the window ... i think).
The obvious upgrade would be to a GT TDI 150 engine & then map it.
Is there anything else that you could throw in there easy enough & relatively cheap enough?
How much work is involved in switching to the GT TDI 150? While the engine is out, does anything else need replacing? Is it wise to upgrade certain other components while you have access?
He mentioned the TDI 170bhp. Isn't this from the MK5 Golf? I imagine there'd be a fair bit more work fitting that in than the GT TDI 150 from the MK4?