The 6.2 vs 5.3 is night and day difference.
My heads/cam/headers 5.3 did 0-60 in 7.25 seconds.
My 6.2 with mods in sig did 0-60 in 5.3 seconds. So much more power that the front diff is now whining lol and my A/C compressor is going out now.
The part throttle is where you get the biggest gains, which is where you drive 99.99% of the time. It just scoots up to cruising speed without issue.
With that being said, it's not that cheap once you get a junkyard engine or GM crate engine. Hindsight being 20/20 I would have just bought the Denali for like $6k more at the time. It is what it is though.
I am likely going to demod it a bit because the cam/headers do make it too noisy/smelly for the young family. Even with the cats, it smells a bit out the tailpipe.
Stock 5.3 exhaust will Choke it immensely. From what I recall, the exhaust manifolds are identical but the 6.2 has a bigger Y-pipe and a 3.5" catback.
I am using the Corsa 3" catback, but it's straight through so it should flow as good or better than the stock 3.5 with chambered muffler. Of course, if you can get a stock 6.2 3.5" exhaust, that would be ideal. I have scoured ebay for months and never found one that was cost effective. It's rare for people to take these off since the aftermarket ones are generally smaller pipes.
With that being said, if you get the big Y-pipe, 3" should be good enough at that point since the further back you go in the exhaust the less the pipe size matters. At this power level anyway.
Magnaflow is one aftermarket one that is the full 3.5" with stainless steel pipes.
