My daily driver - 97 Furd F150 4.6L. 4x4. Air Raid cold air intake and K&N filter. OBD reprogrammed for harder shift and performance at 87 oct. (No chip) Engine replaced 2 years ago. 10K on new engine. I took off tonight from a stop sign fairly hard. About 3500 - 4000 RPM engine started popping and missing. No check engine light. I then noticed hesitation on accleration and slight miss. The miss was not regularly occurring. Still no check engine light. Would a REAL DIRTY K&N filter cause this? Any ideas on what would cause this????