fuseone

which has better peformace/sound. A exhaust system or a cut out for a ls1. like i want somthing that has a loud deep sound. but also get some peformace out of it

300bhp/ton

It's an exhaust SYSTEM so to maximise potential you'll need to whole thing. A cutout just by-passes a section of the exhaust and can be of benefit or not depending on the setup.

LT headers, Y pipe and catback

or

LT headers X pipe and duals

Both work well.

fuseone

what if i was running long tube headers and cut out

300bhp/ton

well it still depends.

If you want a technical view on this read the sticky on exhaust/induction mods, there's a link in my sig to it. Read posts 6 and 13 onwards.

Essentially this area of the exhaust is about flow. A cutout by-passes a restrictive section of the exhuast. However if the muffler on the car flows as well or better than the tubing then by-passing it will see no gain in flow and no gain in HP from this aspect.

There is such a thing as the exhaust pressure wave. Affecting this will affect HP. A cutout may have a posative, negative or no noticable affect on it. It depends from setup to setup.

The other aspect of good exhaust tuning is scavenging, this is what LT headers do. The mid pipe (X, Y or H) also scavenges and generally will promote more HP. If you by-pass the Y on a regular catback system then you may loose power.

But if the tubing after the Y pipe is restrictive such as 2.5" then by-passing the Y will loose out on scavenging but gain in flow. So you'd probably see better over all results.

Sorry for the indirect answer, but there simply isn't one solution as each individual setup from air filter to exhaust outlet will vary what is best.