What are your egts? These early banks turbos aren’t bad for 15+ psi if you put a larger compressor wheel and housing on them to match the larger exhaust housing, one of my customers used a stock 7.3 with an unmodified ATS 088 (similar turbo to the early banks, big exhaust housing and wheel, small cold side) and my db2 tuning guide to make over 400hp with a little spray. Kinda copying the shop truck’s old setup, and currently the stock engine/turbo power record:
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Most people aren’t looking for big numbers like that, so if you’re going for better low end performance a smaller exhaust housing might be in order. It’s also likely that your compressor housing isn’t ideal for what you’re after either. The stock cast wheel is about a 54/64 and the housing is a .70 AR. When you go to a larger wheel, you decrease the AR even more since the AR is a value for the ratio of housing area to wheel area. With a 60-1 wheel, you’re going to a 60/76 from the 54/64, so I imagine your AR to be close to .5 now with that much of an increase, where the turbine housing is a 1.00 AR. I think your turbine and compressor wheels are a good combo, it’s just the housing match that doesn’t seem to be working.