For a better power gain witch is better bellmouth or a divorced down pipe both would be catless in my prefrence so whats the best one to choose if i also going to a catles strait pipe high tubro back exhuast

 

Neither one will make more or less power. The theory I believe is the divorced downpipe will create less turbulance on the wastegate, and hence potentially reduce boost creep. I dont think it matters either way as long as you get a bell mouth DP.

Figure out who is going to tune your car and see what they think.