Allen at Nelson tuned it, it's a 6.0L. It does pull better up top, but seems sluggish down low. I plan on a cam real soon, but it is a relatively stock engine until that. I also have an x pipe with no mufflers if that makes a difference.

 

Your cam swap should wake it up, get a good converter and you'll be looking for stickier tires.

 

Gears would make a big difference to. Sig shows a 5spd trans. I noticed significant low end gains with mine on a pretty much stock 5.3 and no tune. The lack of mufflers might be a factor? Not enough backpressure? Most of us run an auto trans. as well so don't know how much of a difference that makes.

 

5-speed mybad.

 

Both of us complaining of a little low end loss and he has no mufflers, I have a loudmouth one(so basically no mufflers). Could be the problem. I will update later this week when the magnaflow is on.

 

Thanks for all the replies everybody. Keep them coming if you have anymore thoughts on my dilemma.

Yeah, let me know how that goes for ya. If it helps I'll be running out to get a couple mufflers.

 

i didnt lose anything down low with my 5.3 when i added longtubes. had time slips to prove it.

 

Go check and make sure you didn't crack a spark plug or fugup a plug wire like I did...

 

I have a stock 5.3 with OBX headers and did not notice anything from them.
I think I might even have lost some with them.

There was no change at all in airflow in EFI Live, but that was not in the same conditions.

The top end seems the same as it was stock. I think the OBXs are a 3/4 primaries.

 

This was with the stock maf and airbox.