my '02 SS w/ 50K has always started up somewhat roughly but only for an instant. My mechanic tells me its fine.

Today I had the oil changed and struggled to get the oil change reset to work. I must have pressed on the gas pedal 15 time in a row before it changed.

When I turned on the car the start was silent and smooth. No clunking or shaking. Is it possible that the fuel pressure is dropping when the car sits? Maybe my pumping the gas helped that? Could low fuel pressure at the rail cause the rough start? I'm not sure if fuel injection works that way.

I had a moment of panic when I turned the key. Years ago I forgot about the kill switch in my '77 Monte Carlo after a Padres game. I sat in the parking lot constantly turning it over and pumping the gas until I remembered the kill switch. With the kill switch turned off, I started the car an promptly blew the muffler right off. The skin of the muffler just peeled off and flew across the (luckily empty) parking lot. Nothing like that happened today.

 

You can put a gauge to the rail to measure the pressure. It should hold pressure for about 10 minutes or so. I guess you have an aftermarket radio? I remember doing that with my impala to reset the oil.