about 2 months ago i swapped in a '99 JDM SiR B18C into my '98 EK. my motor setup is as follows. B18C, Skunk 2 IM, DC 4-1 Header with USDM cat, CTR b-pipe, and Spoon N1 axle back. im running a JDM P73. when my motor is coasting in gear at around 2-3k rpm i tap the throttle to accelerate again and it will 'pop'.. im guessing its back firing.. i changed the O2 sensor thinking it was that.. no change. so im guessing its loading up with decelerating and, obviously, pops when i get back in the throttle.. any insight as to what i can do to fix my problem would be great.. thanks!