I have the pettit hf cat but it seems like when Im boosting that the airflow is being greatly restricted, would that be the hf cat or what else could it be

 

not sure but it could be the cat. someone did a test with a Random technologies, Bonez, and pettit cat and the pettit broke the first week so they replaced it and it broke again. I would go with the bonez they said it worked well. BTW do you have a downpipe or the stock precat? that could be it.

 

I have the dp that came with the apexi kit, I replaced the hf cat with a new gotham racing midpipe, and a new n1 catback, and the problem is gone

 

On my car I re-install the cat one day a year for emissions testing. It is not the stock one though. I use the Bonez cat. The power difference between even a high flow cat and no cat is staggering. With the cat, flow gets restricted enough that boost response is slowed down. More lag. Also since backpressure after the turbo takes twice the pressure on the compressor side more or less to overcome it, it takes a few more psi to get back to the same power level that I had without the cat. A very restrictive muffler has the same effect. It looks like you just found this out with your pipe switch.