Did you run a cutout or anything?
The pacesetter has bigger collectors and y-pipe not to mention no cats in the way so you will gain some more power from em.

 

The obx has no cats. I ran a cutout. It was too loud lol.

The biggest gain with the headers was with the cutout closed. On the stock exhaust the cutout is a HUGE gain. When I cap the cutout I lose so much lowend, it feels like a 4.8L . With the headers on, I could close the cutout and have about the same power as with the stock exhaust and cutout open. I had my lowend back and I could cruise in an almost silent cab! I'd say the headers got me a solid 15-20rwhp. Parish demonstrated a 15rwhp gain with just a cutout on a stock LQ4.

 

Does the grinding noise happen while it's cranking? If so, I'd have to say that something is up with the starter gear not fully extending. The ends of the gear do look to have some wierd scrapes on them

Sounds like you found your rattle, sorry to hear that you're back to ditching your header set up, hope you have better luck with the PaceSetters.

 

Thanks Bud. The grinding sound is right when the truck cranks over. I guess I did get a crappy starter. I'm going to pick up a used starter off LS1tech. Should be able to get it for $50-75.

 

I wonder if the starter gear/flywheel is different on the 6.0? Maybe the gear doesn't get deep enough into the teeth on the flywheel.

 

Nope, we pulled off the LQ9 flexplate and put my 4.8L on there. Shouldn't be any issues with that. Although, the starter that I have in there right now is a 6.0L specific starter. The LS1/6.0L starters are 1.7kW versus the 1.5kW of the 4.8/5.3 starter. But I dont think there are any physical differences between the starters.