Engine Performance problem
1997 Infiniti Q45 V8 Two Wheel Drive Automatic 170000 miles
I had a misfire and changed the spark plugs along with the valve cover gaskets due to oil found in the cylinders. It was running rough before the the spark plugs were changed. After the the test drive it took off like a champ. After a while it started doing the same thing as before so I turned around a went back home. About 1 mile from my house the car started to sputter and lose all power. I made it home, and somke started coming up from under the hood. Opened the hood and saw the catalytic converter glowing red. The next day I removed the cat and drove it to see if I had a bad cat. Same thing happened. It took off good, but this time it started sputtering and losing power sooner. When I got to a red light the car turned off. I started it back up and made if home. The car still starts, I just haven't driven it since then. It's been sitting for about 3 days now. Can you please point me in the right direction.