[muddog321]

First make sure that the overheating was only the cap and hope you have changed that Dex cool every 3 years or so and are not loosing any coolant due to common lower intake leak. The misfire could (might) be the injector poppet sticking and you can try some strong fuel clener but normally it requires the upper intake be removed and each of the 6 injectors be cleaned by a GM procedure and then if that fails replace the bad injector - or just repace #3 or replace the whole system with the newer MFI for about $200 yourself. Search the posts for info on all that.