if you do put a TD04 back on....spend a few hours on the exhaust housing with a die grinder. I had one that I didnt much care about...had a few cracks and was just a shitty tdo4 so I hooked into it and made the manifold evo size...the the entry into the exhaust housing...also evo size. Went as far into the scroll section as I could get and opened that up. I also enlarged the outlet area around the exhaust wheel about 1.5mm to let more gas through...works a bit like clipping. After all that ...I looked at the crappy dump...that got a fright too! I evened out as much of the tight radius bends as I could and opened up the outlet to where the exhaust bolts on.
massive...difference. It still comes on boost around the same revs...maybe a bit later. but holds it at least 1000 rpm longer.