So... I have a 2002 Taurus SEL with the 24 valve DOHC engine. I've had it since new, and it's been, for the most part, a good car. I has almost 200,000 km on it. We were on a roadtrip (about 5 hours) to Owen Sound awhile back and suddenly the car had no power. It couldn't even effectively climb a slight hill at 80km/h. It sounded like it was misfiring. I stopped, got out, and poked at the engine. I unbooted and rebooted each of the 3 spark plugs you can actually reach. After 2 or 3 minutes, I got back in and we resumed our trip and the car behaved normally. Since I was at 200k KM and this was the change interval for the spark plugs, I decided to start with them. My buddy's taurus (a 2001 SE) was able to change them with some U-jointed ratchets, but my 2002 doesn't have COP --- it has a coil pack which makes removing the pleanum necessary --- so I did. So I bought a set of the pleanum gasket just in case and did the repair. After replacing the spark plugs --- no real issues found there save the fact that all the old plugs were fairly worn, the car continued to misbehave. Now: the new pleanum gaskets had been a fair pain to repair and the car's behaviour tended towards a vacuum leak (-ish). So I removed the pleanum again a week later to find that one or more of the gaskets was askew... and that they didn't really fit. So I bought another set of gaskets from another parts place and they fit better. Got the pleanum back on, with all it's hoses and now... the problem has changed --- it runs very rough at idle and almost flawlessly at anything above idle. I've sprayed break cleaner all over the engine --- anywhere I think there could be a vacuum leak. No change in revs due to the cleaner. At this point it idles very roughly, it throws P1131 and 1151 at idle, but it drives well. It also backfires a bit at idle --- at least I think that's what the "pops" are. Help?