Is Exhaust Housing Too Small
 

Have been using the TO4e turbo for quite some time in my mild ported 13B. The turbo consist of a 57Trim(TO4E) compressor wheel & 0.60a/r housing, mated to a
HT-18 turbine housing that was bored out to fit the TO4e's turbine wheel. Recently found that the turbo was not boosting well, and decided to take it apart, and found that the fins on the turbine wheel to be chipped off. Anyway, managed to get a FOC turbine wheel to replace, but it is a 76trim(TO4r). So have to re-bore the HT-18 housing to fit this. My question is, will the HT-18 housing be too small for airflow? What is the A/R for the HT-18 Turbine housing? And wikk this setup cause any problems?

Pls advise.

Thanks,
Seven