my 2000 buick park ave started some rough idle and the check engine light came on, also there is a rotten egg smell, is that the cat converter? and will that make the car idle rough?

Code is probably a P0300, random misfire. Probably due to the FPR dumping fuel into your intake.
The rotten egg smell is from your cat due to a rich fuel condition.

You can check yours by watching this...

thank youn I will check that out tomorrow

I have watched the you tube video that Mike sent the link to me, so this morning I went uot to start the car and took off the vaccum line to the fuel pressure regulator like in the video, I waited 5 minutes and no fuel came out while the engine was running, I wanted to take off the oil filler cap while the engine was running but it would NOT come off, I had to pull really hard and it came off, when it did I could tell there was a strong presence of vaccum, I put the oil filler cap back on it and could feel a strong vaccum, it almost sucked the cap out of my hand, I am at a loss as to what that could be???????

I have a 2000 buick park ave 3.8 non super charged, was having some issues with rough idle, and the check engine light came on, It was time to replace the upper intake and i ,,wanted to replace the lower intake gaskets, I got that done, started the car and it ran fine, changed the oil and started the car and it runs very rough, I took off the oil filler cap and it would not come off, I had to pull really hard to get it off and when it did come off there was a very strong presence of vaccum, I went to put the oil cap back and it almost sucked the cap out of my hand, I am at a complete loss as to what this might be?

Check the PCV valve and system.

PCV......Only need one thread for a request.

Yes, please do not create multiple threads with the same topic. Merged them together.

sorry about that, is there a way to cancel multiple thread?

I relaced the PCV and was able to use a scan tool from oreilly auto, code was P0300, still runs rough