[Shotimes] CHECK ENGINE On Deceleration

[Peter Maggiacomo]

Funny thing started today, with the CHECK ENGINE
light coming on while decelerating from 75 in 5th 
for an exit ramp. It happened 3 times and all in the
same conditions. It's only on for 5 seconds at the
most.
Another annoying problem cropped up today while
driving
in city type traffic. When in traffic and the light 
turns red and it's a clutch and brake senario, the
engine stalls. This is with the AC on. I've had the
car 5 days from picking it up with new AC compressor
and lines, and it never did this. The only thing that
may or may not tie into this, is that I just filled
the tank with gas. Could poor fuel cause this?
It all started after I got gas, but it could be non 
related. Thanks.
-Pete