I have developed a problem... when lightly accelerating my car will bog down and hesitate really bad before moving. It doesn't do it all the time. In upper rpm's or in boost it runs fine. I put the stock cat back on in order to get rid of the CEL being on all the time and was wondering if that is the cause? I never felt it with the test pipe on. Anyways this is what I have

00 si
stock pulley but hits 8lbs
fuel pressure static at 44psi under boost about 78psi or so
thermal exhaust with stock cat
dc header
short ram intake
btc set at 12 o'clock
walbro gss342 255lph pump
bkr7e plugs

if you can think of anything I would really appreciate it since it is driving me nuts.