2007 Mazda3i ATX Sporadic and sluggish throttle response
 

Hi guys! I have a 2007 Mazda3i ATX sedan and have been having some weird throttle issues lately.

It seems at random times when accelerating it will either be very sluggish and catch at random intervals. Or it will accelerate and drop off and back on quickly randomly as I go up the rpm curve. I've noticed a repeated instability when pulling in 2nd gear just before the 4k rpm mark. And a random chugging through 3rd gear.

I pulled the plugs a few days ago and they were reading lean, and the gap was off, so I put in a new set of NGK Iridiums and gapped them to factory spec. I've changed my intake and exhaust setup so I imagine that's why the plugs were lean. But i'm still having throttle instability days later.

I have no engine light and checked for codes earlier and there are none.

Any ideas?