Bad Gas?

[vex]

I'm having some trouble. Here are the symptoms and the start of these problems:

this was about two months ago:

For the past few days I've been having an intermitent problem of a rough idle. Bad shaking, lack of power. Yet if I drove it around the engine would just come back to normal for a time. Happend when I put in some gas from a local gas station. Figured it was just bad gas. Filled up with different gas (same grade) and the symptoms went away. Felt good for about 4 days. No rough idle, no lack of power. Everything was normal.

Then yesterday on my way back from work, the symptoms showed up again. Lack of power, rough idle. So I took out my spark plugs. Monster fouling. Lots of carbon build up. I cleaned out the plugs and re-installed. Tried to go to work today and the engine ran fine. No problems until I got onto the highway. Then the symptoms came back. Rough idle, lack of power. Basically feels like I'm running on one rotor. Pulled off on the side of the road right as the car died. I pulled off because I kept hearing a metal noise like a lp banging against something--I wasn't sure what it was so I got off as quickly as I could.

On the side of the road I waited for the engine to cool. I pulled the plugs again, and inspected. No fouling (There shouldn't be anyways I hadn't gone more than 10 miles), and they weren't coated in anything--oil or otherwise. I let the engine cool a little more and removed the pressure cap from the radiator to see if I lost a coolant seal and I seemed to remember that an easy way to check if I lost a coolant seal was to open that cap and crank to see if I got any bubbles/splatter. Nothing bubbled or splattered, so I assume my coolant seals are okay. Next I pulled the plugs and turned the engine over by hand. I got 3 strong "whistles" from the front rotor, and I got little "psssshhh" from the rear. I kept turnign it by hand and I eventually got 3 strong "whistles/psshs" from both front and rear.

I called into work today to let them know what's going on so I plan on doing a compression check in an hour or two, and if that checks out, looking for a vacuum leak. Is there anything else I should look for?

something recent that might affect this might not: I ran out of gas about 2 weeks ago. I doubt it has anything to do with anything since I had replaced my old fuel filter with a new one about a month or two before that. Another thing is that I continue to get condensation in my oil tube, but I clean it out regularly and it hasn't had much trouble with it recently. I think it was oil in the line I replaced.

The car itself is an S4-NA mostly stock (only suspension modifications)
Gutted Cats
Recently cleaned (<10,000 miles) injectors
Silicon Vac Lines replaced same time as injectors.

Cliffs: Car ran fine after having an intermitent problem of Rough Idle and lack of power. Today car died on highway refusing to restart. Heard metalic noises from the front of the car (which didn't happen at all when I nursed it back home). Coolant seal seems good (unless I opened the wrong cap and did that test wrong). Compression seems useable--will know for sure later today. What's wrong with my car?

After that day I checked compression and had 115 on both rotors with 30psi individual pulses and the shrader valve held down.

I drove the car around and got some better gas in it from 7-11 and it behaved itself from there out.

then yesterday the symptoms came back. I was able to nurse it home and pull it into the drive way. Went digging in the engine bay and roughly set the idle. That seemed to cleaer up the problem. Drove to work today without issue, and then while driving home all of a sudden while cruising in 5th the symptoms started all over again. Now I can't get it to behave itself again. now this is after I filled up at a 7-11 up in gainesville two days in a row. I'm wondering if it's possible that I got bad gas from a store that I usually do not have a problem with?

Any suggestions or insight into this?