96 A4 , Having some issues. Stalling, etc

I am thinking about buying a friends 96 A4 5 speed with 100K miles.
During test driving, the car would stall occasionally when coming to a stop. It would start right up again after.
When the AC was on, it would stall more often.
Also, while driving, when you let off the gas and depress the clutch to shift, The rpm would take about 3 full seconds to drop to idle speed.
I also noticed a rich smelling exhaust but no check engine light was on, interesting i thought.
I then checked to see if CEL was functioning, and it was NOT. It does not come on when the ignition is switched on.
I am wondering, what could be possible causes of no cel coming on at all?

I guess i should have it checked for codes next but was wondering if anyone might have some ideas about what is going on.

Any help would be appreciated.

Thanks

Al

Sounds like EGR Valve is clogged up.. causes rough idling....