i recently installed a 3.5' mps, and ever since, at high boost have been getting a popping in my intake. it is blow back, but i don't know where to start to try and fix it. i am hopeing i am not floating valves, but since it only started after i installed the smaller pulley, i don't think thats what it is. any help/ suggestions would be helpful.

Do you have a scantool? If not, I suggest you pick one up and check your numbers out. Any SES light on at all? And you are using 91 or higher, right?

You changed your plugs when you installed the pulley? Double check the wire routing.

A smaller supercharger pulley allows you to push more air into the motor. It does not seem logical that it would cause a backfire of any kind. Unless there was a pre-existing problem or something occurred during installation like a plug wire being crossed.

Just to throw this out there: Could it be that the plug gap is too large for the added boost?

i installed the plugs about a month ago, so it'* not crossed wires. i was talking to my father, and he thinks it may actually be a lean pop. i still have the stock airbox on, and that may be restricting the airflow. not sure if that is it or not, but i am going to be getting a fwi hopefully soon to see if that takes care of the problem. as for the gapping issue, i have ngk iridium ix'* installed. i have them gapped for stock, so i am wondering if that gap being setup for stock boost is a problem, and what that would cause.

oh, and as for KR. It maxes at 2 at the top end of gears at WOT.

For a short while I had Accel coil packs that would do that.

Ok..

Does it appear to run less than smooth? The stock intake is only a minor restriction that shoudl not cause this issue.

Remove the valve cover cap and try to duplicate the issue. Do you have a way to get the data scanned from the car to see if it'* running lean?

well 2 new developments/thoughts..... the first is my exhaust is extremely restricted, so probably a bad cat. The second thing is that i believe the stock gapping on my plugs may be causing the popping at high rpm. This is what i think is causing the problem, i will find out in a couple days when i replace the cat and regap the plugs. i will post if this fixed the issue or not.

The stock gap isn't causing any issue except maybe a little predetonation and you aren't experiencing KR at shutdown.

Get that exhaust fixed. Most likely it'* the problem.

well, i replaced the cat, regapped the plugs, replaced o2'*, and put a cai on, and i still have the popping. the popping occurs under heavy load, in the middle of gears. on the top end of the gears the popping disappears.... later today i am installing a performance plug wire set, and an intense pcm to see if it helps any. I am not sure if it will help, but the intense pcm will make the car more fun. i also have been experiencing KR in first gear starts at 0 works up to 1, in second it is 0-1-2, then when it shifts into third it is 2-3 and i haven't held WOT too far into third, as i would have to drive over 100 to check this out.

please post any thoughts as to either issue of the popping or the KR
thanks in advance
Justin