you'll get more out of the car with a tune, but you don't "need" a tune at the basic modification level. It wont lean out enough to factor in. It will still knock 4-6 on the factory tune and GM is ok with that amount.
This, and hello Phil!
Your just leaving power on the table if you don't have it tuned. Add some LT's and don't look back! If your an automatic, then you will love a transmission tune.
Forged bottom end. AGP TT, Dual nozzle meth, ID850's, Livernois dual fuel pumps, ECS BAP, 25% UDP, 3 inch Magnaflow catback with X pipe, Mantic 9000 clutch, DSS 1000hp axles, DSS aluminum driveshaft, ZL1 rear end, solid subframe bushings, HE differential offset bushings, BMR Trailing arm, BMR toe rods, Lingenfelter LNC-2000,SJM Line Lock, and much more Built by, FSP, myself, and some a few others, Tuned by FSP and me 800ish whp