Your software was most likely off which is normal when you start modding an engine.
The only way to measure fuel economy is manually log the mileage and amount of fuel consumed. Sorry, but you didn't get 27 mpg unless it was for only a couple miles downhill.
Correct. It's just hard to believe you're ACTUALLY getting 7-10 MPG better than everyone else with the same mods.
1969 Chevy RCLB C10 350/TH400 SOLD
2007 Chevy RCSB 4.8 4x4 LS SOLD
2008 Chevy RCSB 5.3 4x4 LT SOLD
2010 Chevy CCSB 6.2 4x4 LT SOLD
2005 GMC CCLB DRW 6.6 Duramax 4x4 191,000 and counting
2013 FORD CCSB F350 6.7 Powerstroke 4x4