I have an 89 IROC-Z with the L98 and when I bought it, it had stock exhasut manifolds, out to dual cats, then back in a Monza 3'' Pacesetter catback.

I just got SLP 1 5/8 Jet-Hot coated headers installed and I let my friend drive it tonight so that I could hear it. The results were quite surprising. With the headers, the exhaust is actually quieter now!!!

How is this possible???

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1989 Chevrolet Camaro IROC-Z
L98 - 350c.i. TPI, rebuilt 700R4 auto w/shift kit, Dual catalyst Monza PaceSetter Cat-Back, SLP 1 5/8 Coated Headers, 3.23 Posi rear, Accell 8mm ignition wires, MSD 6A Ignition Box on order, Hypertech chip with 160stat, Under-Drive pulleys, AFPR, K&N's, !Air Box w/ Ram Air, moddified MAF, throttle body coolant bypass, Spohn SFC's on order, Alarm, Keyless entry, remote starter, 92 Z28 AeroWing, Brand New Paint (6/21/01)

Future: ZZ4 TPI w/EGR, T56, 3.42 or 3.73, Spohn strut tower brace and LCA's

1989 Chevrolet Celebrity Eurosport
2.8 MPFI, no mods
225,000 miles and still ticking!

More info and pics on my webpage:http://go.to/iroc-z

AOL IMer: GPA 0point0

[This message has been edited by L98IROCZ89 (edited August 15, 2001).]

 

Maybe there was a leak somewhere between the engine and the cats that got fixed when you replaced all that?

Just a thought..

 

clogged up cats?

 

Thats wierd, I know putting headers on my car made it sound MUCH louder and meaner......not so much at idle, but definitely when you open the throttle.

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Z28 Grille w/aftmkt fog lamps, MacEwen white-face guages
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, 3.42 gears w/Torsen posi

 

Just out of curiosity what have you run at the track l98?

 

I ran a 14.4 @ 96 mph with stock exhaust manifolds, the muffler removed from the cat back and without the ram air, TB coolant bypass, hypertech chip, and 160 stat.

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1989 Chevrolet Camaro IROC-Z
L98 - 350c.i. TPI, rebuilt 700R4 auto w/shift kit, Dual catalyst Monza PaceSetter Cat-Back, SLP 1 5/8 Coated Headers, 3.23 Posi rear, Hypertech chip with 160stat, Under-Drive pulleys, AFPR, K&N's, !Air Box w/ Ram Air, moddified MAF, throttle body coolant bypass, Spohn SFC's on order, Alarm, Keyless entry, remote starter, 92 Z28 AeroWing, Brand New Paint (6/21/01)

Future: ZZ4 TPI w/EGR, T56, 3.42 or 3.73, Spohn strut tower brace and LCA's

1989 Chevrolet Celebrity Eurosport
2.8 MPFI, no mods
225,000 miles and still ticking!

More info and pics on my webpage:http://go.to/iroc-z

AOL IMer: GPA 0point0