Sound Stock Cam???
Headers:
Shorty headers are available but pretty much a waste of cash IMO. 98-99s may get a tiny benefit.
Long Tubes are the way to go. SLP & FLP offer systems with interchangable cats & ORP. Other headers can be bought with high flow cats in the Y-Pipe, or you can buy high flow cats and weld them in.
Click on a couple sponsors and peruse what's available.
In my camaro I have a TR224 on a 114lsa idling at 800 through longtubes and it sounds like it has a mild cam...probably enough for a dealer to tell.
If you have headers, you could always just tell them any audible lope is due to the headers making it sound like that (the headers do amplify the effect a lot)



