I wouldnt buy spintech. after having there mufflers rust from inside out in 5 years, they told me that was normal life for there stuff. That didnt sit well with me since it was my daily driver. I switched to magnaflow and will buy that for my camaro as well.
There's loud and there's obnoxious and everybody has different tastes, tollerance level. Flowmaster drones and I'm not a fan (although Raj's car sounds awesome in vids). Magnaflow have a throaty, muscle car growl and I like 'em. Borlas have that 'i kick a$$' sound IMO. Here's an LS3, x pipe and Borla XR1s:
I dunno if I agree 100% on the dumps blowing crap everywhere. Are you driving on dirt roads? I know I don't. Are you trying to keep your underside pristine? Questions for you to answer.
Anything with a decent power level (500hp+) I would go 3".
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2004 NASA AIX Mustang LS2 #14
1964 Lincoln Continental
2014 4 tap Keezer
That's going to make good broad power. The downside, to me anyway, is the car will rock in rhythm with that cam. Kind of hard to describe but it's based on my experience with these engines. I can hear it in the lope. It's just something I have noticed with some cammed LSx engines from the beginning as compared to SBC's. I honestly don't know why the engines are more prone to doing that. I think it may be the firing order of the engine or maybe it's the fact that LSx engines can handle a much larger cam and still idle well compared to a typical SBC.
As for diameter, I'd go 3" with 1-7/8" primary headers unless packaging is going to be tight. Then you might look into 2-3/4" pipe. That might be a lot harder to get your hands on.
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Trey
Current ride: 2001 BMW 540iT soon to be manual swapped.
Former rides: 1979 Trans Am WS6: LT1/T56, Kore 3 C5/6 brakes, BMW 18in rims
Don't do dumps if you can. It will probably smell like exhaust inside the car and tailpipes will quiet down the cabin noise alot. Maybe 3" Intermediate pipe to mufflers and 2.5" tailpipes to sneal around the G-link would work.