02 corvette adding headers

I installed headers a little while ago and im running lean, so to counter act the lean codes I used the predator to add more fuel in the PE and everything atleast by 5-7% and I did some logging and im still getting lean codes, the car feels better but now it idles a tad rough. I don't have my rear o2s installed as of yet [so the o2's are always showing with the lean codes]. this is a catted set up. I ordered spark plug extenders to weld on, would this end my lean code problems? or should I just take it to a tuner?

also I bought a pc interface kit. I don't know if works with my programmer, I tried installing it and hooking it up but it did nothing

[mikel]

ideally, you need a tune to get the most of the headers, and likely to get rid of the codes, what codes are they exactly?