I have a full exhaust (LT's/cats, and Bassani cat-back) on my 03 L with a KB (16 psi), cai, and alcohol injection. I just added the exhaust and honestly cannot tell much of a "seat of the pants" difference at all. If it's gained 20 rwhp I'd be surprised.

My problem is the interior noise; I had LT/cats before with the Eaton and sold it for this very reason. I drive this truck 20K miles per year. At certain rpms it is annoying, although this Bassani setup is better than my prior Magnaflow. I even added some resonators which helped but it's still more noise than I want. Now if it had picked up a bunch of torque/power I could probably live with it.

My question is which is the weakest link in the factory system; the manifolds or mid-pipes and 4 cats? I will either put the cast manifolds back on and go to a hi-flow 2-cat mid-pipe, or do the shorty Bassani header with factory 4-cat mid-pipe. Or just put the stock manifolds and mid-pipes back on with the Bassani cat-back.


Any thoughts?

Jody

 

I'm curious about this too.

My guess is that the stock cats are 40% of the restriction and stock manifolds are the other 60%. The stock muffler doesn't seem to be a restriction though.

 

Just add some sound deadening material....

Coldie

 

I did the rear panel already and it made no difference. Figured since the nmufflers are behind this and there's no insulation here from the factory.....will probably try the floor next, but have my doubts.

Jody

 

My guess would be that the cats then the manifolds as the biggest restrictions in the stock system.

 

Thanks Leonard, that was my first thought from posts about people swapping the mid-pipes and getting good gains. The manifolds should quiet it down quite a bit.

I'm just surprised that the LT's/cats didn't make a very noticeable difference with the KB and 16-17 psi of boost! I noticed the same thing before with the Eaton, but I thought the KB and the way it moves air would be different.

Jody

 

I have Bassani shorties and Bassani catback system (stock midpipe) The combination isn't annoying at all, which is what i wanted because i drive 20k a year also. My guess is that most of your noise is from your long tubes. Good luck

 

Thanks! Well, there another thread about a guy who swapped out the factory 4-cat mid-pipe for a high-flow 2 cat setup, keeping his stock manifolds. He claims a noise increase of 40-50% and that it may be annoying at cruise speeds. This sounds like what I have already, so most of the noise increase seems like it's coming from the 4-cat to 2-cat swap. Maybe just stick the stock exhaust back on and be happy, albeit with a little less power.

Jody