I installed and 3 inch flowmaster cat back, on my 89 iroc LB9 (stock except afe air filters, cut air box, and other minor mods) and it appears to have lost lowend power, my friend says it is because the sound has changed, I now notice it more. Then I removed my air rails and blocked them off, now the whole exhuast tone changed ( sounds tingy at high rpm ,almost volkswagon like?) and I feel I have lost more low end power what is going on?

 

did you remove the catalytic converter? or is it still there?