i have a 98 3800 it has the flowmaster 80 series kit im thinking about getting the SLP kit trying to see what people think is the better kit or in there opinion sounds better

 

I think the SLP Loudmouths sound terrible on V6's. It makes them sound very ricey and high pitched. If you are wanting to change your exhaust around, I have Magnaflow's catback, which sounds great. I also like the sound of Dynomax's catback as well.

 

A buddy of mine had a 3.8L and put the Magnaflow system on his and I wasn't a fan of it once it wound up. At idle it was fairly quite, but the purr was there, then once he accelerated I was turned off. Raspy, just frankly loud, not too much tone or distinct sound to it. I wasn't a fan.

I have the American Thunder Flowmaster cat back exhaust and I NOW like it. At first I did not, coupled with a bad install and the promise on the Flowmaster site to "Have the rumble of a V8", I was let down.
No matter what anyone tells you no exhaust will make it sound like an 8 cylinder. Or a 4 cylinder. Or a 12 cylinder. Each have distinct sounds and trying make one sound like the other is kinda moronic in my opinion. If you want V8 sound, buy a V8. There's no imitation.

However, as I've grown with the car, the Flowmaster sounds good. I like it. It's never pingy or raspy, it has a tone to it, and through the whole range it has sound and not noise.

As for power, I couldn't tell much, but I certainly enjoyed having a sound and a nice looking dual exhaust outlet.

Just my 2 cents.

 

Borla:
http://tinyurl.com/mt6bk5