am i wrong or does getting aftermarket exuast better your gas millage?

 

it might alittle but not really enough to tell a difference

 

Put on too large ofdiameter exhaust pipes & your fuel economy might even get worse.. Some think "the bigger the better" and put 3" dual exhaust on their mostlystock car, which will reduce backpressure too much.

 

I have a full Bassani exhaust and it made no difference at all.
The biggest thingI did that helped mileage was to bump the timing.That won't help any if you don't advance the timing from idle.

 

Longtubes, O/R midpipe, and a good catback usually helps it out. But it's not very noticable.

 

greystang is correct, i had the same problem, i had to throw in a h-pipe to make up for a little compression loss. i felt the difference in power but the gas mileage slipped away a little. until i put the h-pipe in it ran like **** too

 

Not enough to really notice, maybe a few miles per tank. Most people tend to be a little happier on the throttle after an exhaust install and cause a decrease in mileage.