87 T getting bad mpg...HELP!

[87TTypeKid]

Ok, the car sat in our driveway for about 2 years without running, but I recently put it back on the road in October. The car was extremely well maintained by my parents since new, then it was turned over to me once they got another car. The car runs and drives beautifully, even under full throttle and full boost...it never misses a beat. However, it seems to be getting relatively bad gas mileage...I only average around 16-17 mpg, even on the highway...I've gotten that kind of mpg on ALL highway driving...as I understand its supposed to be getting more around 24 in those conditions.

Symptoms- under WOT, the exhaust smells very close to raw fuel moreso than burnt fuel. I have a test pipe on the car instead of a cat, and the clamp kinda crimped the stock downpipe a little bit, so exhaust leaks out on the front end a bit. The areas that it leaks out are noticeably black, telling me SOMETHING is making the car run rich. No check engine lights (although one was on and off back in the beginning, and the exhaust was black enough to darken the fenders). What could be causing it to run so rich? I dont notice any leaks anywhere either....

HELP!!! Gas is expensive!

 

[salvageV6]

What chip is in the car?

 

[87TTypeKid]

Nothing is done to the car at present besides a Hooker cat back. Stock chip and everything else, and a Walbro fuel pump with steel braided lines. I'm thinking the regulator isnt functioning properly, or an O2 sensor maybe? Whatever it is it burns reeeeeeeeeallly rich under boost...quite a noticeable difference in exhaust odor.

 

[BlackMetal]

My guess would be regulator since you said it's bad under boost, but I'm no expert.

 

[onefastcar]

Change the o2 sensor first its the cheapest and most likely culprit and do yourself a favor and buy a scantool at the very least it will save a lot of the guess work or the use of part replacement theory out of the equation and help save your gas.

 

[gnxis]

Change the o2 sensor first its the cheapest and most likely culprit and do yourself a favor and buy a scantool at the very least it will save a lot of the guess work or the use of part replacement theory out of the equation and help save your gas.

My thoughts exactly.