I just helped my friend do his zc swap into his 91 si crx everything is hooked up right i've checked it many times ,when he drives it ...It has alot of lag then after about 2500 rpms it gains power and does just fine and sometimes it makes this wired poof sound when were driveing it ,we checked it with the timeing light and its in pefect time anyone ever had this problem

 

That poof sound might be backfire, but backfire is more of a pop sound. Backfire can be from having not cat or running really rich. I had a lot of trouble with my zc bogging on me but it was a wiring mess up that gave me problems.

 

make sure the cam timing is set right. it sounds like you are a tooth off on the intake gear.