Well for the 4.2L, you can go with Borla. That was my first choice but since they didn't have anything for the V8 yet....I had to take a pass on them.
The resonator....don't think that that was taken off.......all the guy did at the shop was to cut the old muffler off & weld on the new one in place & that was it.
As far as the exact extra power....hard to say. I have never dyno'd her & as far as driving differences afterwards.......a little bit quicker....but nothing really noticeable. Supposedly...about 10hp....torque....? got me there. It did seem to get up to speed just a little bit better than before. But since dumb me didn't time or dyno anything....again it is hard to say.
I don't recall any other manufactures at the moment with the exhaust systems for the inline 6. When I have the time, I can get back to you on that. I am just headed to bed right now so I can get up at 4am...YUCK!
All that I have done to mine has made it definetely quicker. Heck, I have had it up to 123MPH

& it was still pulling hard....though it would (very soon after that) be redline limited & the major thing.....tires aren't rated for that amount of speed. I could only do short top end runs & nothing prolonged for fear of overheated tires & blowouts.
It still lacks the off the line boost that I am looking for. But hey...at least it's better than what it was...
K&N makes a nice FIPK for your if you need an air intake. JET makes a chip for yours.......my mind is drawing up a blank right now...so I can't think of anything else right now. Like I said...if I can get some time, I will do some lQQking to see what else is available for you.
Talk to you later.
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2003 TrailBlazer EXT 4X4 NorthFace Edition. Silver Green over Pewter
Every option minus the DVD 4 a MoonRoof.
5.3 V8 3.73 Locking Rear.
Performance:
TrueFlow Air Intake
Granatelli Mass Flow Air Sensor
FlowMaster 70 Series SUV Muffler
Predator Power Programmer
Airaid Throttle Body Spacer
Misc.:
Super White headlights 80W & 100W
Fog Lamp bulbs
Billet Grill
XM
Tekonsha Prodigy Brake Box
Valentine 1 Radar
Line Of Fire 49" L.E.D Brake Light