Recently when going WOT, truck struggles to climb the rpms. By that I mean it's going good then it stops climbing for a sec then it goes. I raced a stock L and he was keeping up cause my truck would go then fall on its face then go and so on. I recently changed spark plugs (NGK TR6 and gapped to .35), fuel filter, delete egr, delete pcv, plug turkey pan, re-route some vac lines, cleaned intercooler, plenum, TB, changed trans filter and oil. Intercooler pump is working fine. Before all this truck was always running smooth so I know I must of done something wrong. Check engine light is on cause of the EGR delete. Could it be the plugs or the Coil packs. Or do I need a tune. Please help as I'm going to put some performance parts and I wanna make sure it's running right before the actual tune. Also, I noticed it backfires a little at times now.