HELP!!!! 96 MOnte Carlo Starting Probs!!!

I have a 96 Monte Carlo 3.1L. I recently had a new fuel filter, spark plugs, wire set, coolant seal/hose etc installed which cost over $800. Prior to this work the car would start fine. But now it will randomly decide to start rough.

For instance, I let the car sit for over 24 hours and it started fine. Left it for 30-45 minutes and it started very rough (ie turns over, idles real hard and then slowly shuts off with the Oil and Volts light coming on but no Service Engine Soon light. Leave it for a minute of so--it starts, idles jumping between 500-1000 RPMs for about a minute and then evens out.) As soon as it starts and gets past the rough idle it will run fine.

Since the latest repairs I have also started using 93 Octane gas (as compared to the 89 before) and I have also had an oil change.

ANY IDEAS?!! PLEASE HELP!!!

PS--the car is consistently parked in full Florida sun as well.

You may have gotten a bad new plug or wire, very possible, especially if you installed Bosch crap. It could be an unrelated co-incidence, but I doubt it. Take it back to where the work was performed and make them re-check their work.