TPI Gas Mileage (longhorn man & any others)

[mocwon]

I went the TPI route for the engine in the 72 hoping to get the 18-20 miles per gallon that I have often heard comes with this swap. I'm getting 12-14 MPG so, to say the least I'm disappointed. I've got to believe I've done something wrong or have a bad combination of some sort. I'll spell out the particulars of the drive train and operating characteristics to see if to see if anyone see's any clues where I might look.

• New 350 GM long block #10067353
• .383 intake lift
• .401 exhaust lift
• .194 intake duration
• .202 exhaust duration
• 112 degree lobe separation
• 8.5:1 compression ratio
• 700R4 transmission
• Stock mass airflow TPI w/cold start injector
• Stock Bosch mass airflow sensor
• Electric cooling fans
• 24# injectors
• 1987 stock Z-28 Camaro ECM and prom
• Painless wiring harness for TPI
• 3.08 rear gears (open)
• 31” tall tires
• 2-1/2” exhaust w/X-pipe
• Stock exhaust manifolds
• 16 gallon under bed gas tank with in-tank electric fuel pump
• 40-43 PSI fuel pressure
• 3/8” fuel feed line and 3/8” fuel return line
• At 70MPH in OD the engine is turning about 2,000 RPM
• I tried running it in third gear and had a very small decrease in MPG
• Engine operates at 210-215 deg F