I bought a 96 SVT Cobra today with 39K original miles. I've been looking at this over 2.5 weeks. I test drove it, had my mechanic look at it, and the owner recently put like 250 miles on it, ran perfect. We go and transfer title. I go to take it home and not being used to a car with an alarm I set off the alarm. We disarm it and I drive home, literally 3 blocks. Runs great, We sit outside house with car idling, AC on, it's purring. It is low on gas but not on E. All of a sudden it stalls out. The check engine light and the Theft light come on. We try to start it. It starts rough, misses, and black smoke comes out drivers pipe. I'm freaking out. 1st I go get 5 gallons of Sunoco 93 and put it in, no difference. So I call the guy I bought it off, I'm thinking stop payment on check. He's cool and drives right over, he's freaking out too. He realizes I drove like 1/3 mile max. He see's what it is doing. He disconnects the battery for a few moments. Starts it up and after blowing some rich gas out of pipe all is fine. He revs it a few times it's fine. I drive it 18 miles, it works great, I fill it with Shell 93 and drive back 18 miles, it's great. Any idea what the hell happened other than to scare the **** out of seller and buyer who are both adults. This car was pampered, kept in a heated garage with a trickle charger. It's a 4.6 with a Super Chip, 5 Speed, New H pipe and flowmasters, no CATS, K&N Air Filter and always run on Royal Purple oil. Something with theft alarm. Could it have run low and drawn in gunk from bottom of tank? It was blowing so much smoke I was thinking rings or head gasket. Now exhaust is clean as can be, runs strong, idles about 800 RPM and smooth. Thanks, Spiney. BTW All gauges were normal.