Strong Fuel Odor

[Westone]

Hey,
I've put about 1200 miles on a reman engine installed in our '98 GMC Safari. It runs fine, it's even quieter than the original due I think to the roller rockers introduced after '98.

Since the new engine was installed there is a strong smell of raw fuel outside the cab (not inside) anytime the engine is running. There is no indication of a leak anywhere that I have been able to find just looking under the hood and underneath the body. It's also difficult to tell exaclty what portion of the van it's coming from.

I'm wondering if it's possibly coming from the exhaust due to the engine running way too rich. Is it possible, with the computerized engine control module setting all the parameters for fuel flow, that the engine could be running so rich that raw fuel is coming out the exhaust?

Possibly related events:
When the reman engine went in, there was a problem with the original MAF Sensor being faulty. The engine ran way too lean until warmed up, then ran fine. A reman MAF Sensor was installed and it has run fine since then (this according to the mechanic who installed the engine and diagnosed the faulty MAF Sensor).

On the first 2 tankfuls of gas, the new engine averaged about the same as the original engine - ~19mpg. On the 3rd tankful the mileaged dropped sharply to ~14mpg. I'm on the 4th tankful now.

Any advice is appreciated.
Thanks,
Bill

[Kings-x59]

Here's one thought:
On my '89, the vent line coming off the fuel tank to the vapor canister had a hole chafed in it. I kept picking up whiffs of gas outside the van. You might check the vacuum lines on the vapor canister for holes or splits.
Not only will you smell gas, but you'll lose vacuum in the system.