95 S600 Coupe failed emissions

[Hatebreed]

Ok, Just got this S600. I paid very little for the car. This is the only reason I even entertained this purchase. The PO reported that the car did not run and was losing all of its fluid. I bought not running the car and it is in excellent condition. Repaired the coolant leak from behind the engine and it run really well. It drives great on the highway and does not stall or even run rough. The only issue is it failed emissions at idle. The idle seems to hunt very slightly and I have a fuel smell from the exhaust....hence the failed emissions. Any ideas on this one? I am more of a diesel person and this car has considerably more going on. Also, I have no check engine light. The rest of the stuff actually works...ASR, some weird shock thing, all the bells and whistles all function. My first guess would be the easy stuff oxygen sensor, MAF sensor.... but I would think I would get some type of light? Any ideas?