Odd noise @ high RPM when trans shifts

Ok , new problem to go along with the unable to locate/fix engine miss. I installed a k&n fipk on the weekend and since then when accelerating at full throttle either from a standstill or once moving, once the rpm gets real high and the trans shifts into second (like normal), the RPM will drop way down(as well normal) and i hear this noise like something bangs against the sheetmetal in the front of the truck(not normal). More specifically is sounds like it comes from the right front of the truck. It will do this everytime when accelerating like this so i was kinda keeping my foot outta it till i was able to make sure i did not have a clearance issue around the fan/shroud ect. All checked out fine, plenty of clearance. Tonight i pinned it to get ahead of a few vehicles (also to see if that noise was still there) and when the noise happened again, something kinda caught my attention. I did the full throttle acceleration again a couple of times and to me this noise sounds like backfiring through the intake and the sound is the loudest at the right front of the truck , right where the wide open k&n filter is. One thing i notice for sure is that since i installed the fipk the truck revs ALOT higher quicker and my question is , can this possible backfiring through the intake be related to the seemingly engine miss and was just made worse by being able to rev to high rpm's that much faster and if not , then what the heck could this now be ? ? any suggestions appreciated.

Well this problem seems to be solved. It was a combination of a couple of things. First off the plugs i replaced about 3 months ago now were AC double Platnium (old stock). Next, the gap on those spark plugs was at .60 (old as well) The Plugs that GM now sells are Iridium (spelling) and the gap is only .40. 3 of the 8 spark plugs were bad as well as three plug wires. You should see the gouges in the porcelin on the plugs , i was amazed that this did not cause a misfire code. With new spark plugs that were gapped @ .60 and old wires (85,500 km's), they could not handle the resistance of such a gap and caused severe carbon arcing. I am still amazed that this did not cause a fault code. I said right from the begining that it felt like a engine miss but they said nope. I say , if it walks like a duck,looks like a duck...............IT'S A FRIGGEN DUCK. So all i can really think to add at this time is this ;.........If you have rough idle , do not always depend on there being a code. This which I have expierenced is proof. If you have rough idle , change your plugs and get the AC iridium AND change your plug wires even if they look good....... i still can not believe with the damaga caused by the carbon arcing that there was no code....................

A Lot Of The Times A Code Will Not Be Set Unless Its Affecting A Emmissions Componnent