tuzzy

here is the deal. i have a 02 z28 m6. full exhaust,tune, a 12bolt, lid, thats it went to the track last year ran best pass 12.6. this year 13.2.

fuel trims are normal at idel off idel bank one is +13. and bank 2 is at 0. i know they are to be as close to 0 as possible but i can not figure out why my car is running fat on one bank.

I checked o2 sensors and i didnt find a vaccume leak. anyone have some advice??