Every LS Equiped vehicle i've put headers on has always picked up MPG (With a good tune of course). 40+hp on a 6.2L is nothing to sneeze about ether

 

I have gained or not loss in past header LS combos,this 6.2 hasnt increased preformance enough to warrent the MPG loss.

I expected 35-40HP gains,an increase of 1-2 MPH gain in marked off area doesnt seem like much

 

I thought that was for me .......

 

What effects did your tune and LTs have on MPG? not dyno tuned I assume?

 

How many miles you got on the truck?

 

This may seem too simple, but I suspect that some of your results are because of the expanded use of ethanol enriched fuel and then possibly the winter detergent packages in the gasoline during these months of the year. My mileage drops drastically in the winter, and I have a live tune too. No headers tho

 

Gonzo, the tune alone should get you more than 1-2mph. It made a huge difference on my truck. Do you know anyone with HPTuners? If so, you can pull the tune without buying credits. Send me a copy and I will compare it to mine and see if there are any differences.

 

I have always had 5.3's with headers never a 6.2 ( i wish) but yes not dyno tuned but tuned by Blackbear with a cable tune .now have AutoCal for the 2010........so he reviews tune after intial install .............. stop and go city driving in both trucks is where my mileage picked up the most after / header exhaust ....... highway 1-2 max I reread your post and see you have 1 3/4 not 1 7/8 headers did you mileage fall off on highway too ? if it did that really is a surprise reduced mileage in city stop and go I have seen that before from too big exhaust especially on a small motor heavy vehicle ......gotta think your tune is off ....... what is rest of your exhaust system ? cats ?

 

cats stock catback,7k miles was winter gas before and after header&tunes.

 

who did your hp tune? no headers? any change with mpg after tune? hp wouldnt show changes made to this efi live at least for comparison sake