Originally Posted by ICEMAN 31
Is your main interest sound or best flowing.
they say and i don't know if its true, maybe RPM can shine some light on this, but there is no catback system that flows better than a cutout and there is nothing that flows better than true duals.
Here's what I can tell you as far as catbacks vs cutouts:
There are some extremely high flowing catbacks on the market. Some flow well enough, that a cutout will offer only very minor gains. For example, one of the best flowing catbacks (utilizing a muffler) on the market that I've seen tested was the old SLP 2OTL (2 on the left) system. Though not popular due to the appearance of the dual left side tails pipes only, it was one of the best flowing catbacks I've ever seen. I once saw a heads/cam LS1 dynoed back-to-back with this catback system and a cutout capped and uncapped....and the gain was only 2rwhp with the cutout open. On a heads/cam car. Impressive, IMO.
Now some catbacks flow like poop, Flowmaster crossflow muffler systems for example. In that case, if you wanted Flowmaster because you like the sound, you're best off getting a cutout as well for preimium power when needed (track, dyno, etc.).
In general, most catbacks will be very similar in terms of flow, give or take a few rwhp. And the cutout will offer some gains, and for the $35 they cost, it's not a bad investment if you want to squeeze out every last HP you can. But you won't pick up massive HP with a cutout on most aftermarket catbacks on a bolt-on LS1 car.
As for true duals, they do offer excellet flow, but the price and (depending on the system) ground clearance issues (especially on lowered cars) keeps some people away. These systems tend to get pretty costly if you want to have the tailpipes run all the way out the back like stock....if you're OK with dumps at the axle, then the price will be significantly less.