In any gear when I de-accellerate around 2500 and below rpm's my car starts to backfire and pops. It feels and sounds like a flat tire. I just had my car retuned with HP tuners, come to find out I am running TR6's and need TR7's. The new spark plugs come in this week. Do you think that will fix the problem with the right spark plugs?

 

Could be the problem...some other things to think about are the tune(too rich), exhaust leak, timing issue. I have the same problem but so far everything seems to be pointing to my tuning. I recently had head work done and my intake ported so I think my tune needs redone. Good luck finding the problem.