I just spent 12 hours installing Flowtech Headers and y-pipe on my '90 Camaro (305, TBI)and the car sounds like I killed it. Installation wasn't a problem, headers dropped right in, y-pipe bolted up fine, cat didn't fit (to long) so just left out for now and just ran it back to my Dynomax cat back system. Started idles a bit rough and a bit louder, tollerable, but when I put it in drive or reverse the sound and vibrations are HORRIBLE. It feels like by car is going to fall apart and the sound will make you insane. Someone HELP! My baby was fine when I before and now it is an undrivable yard orniment.

------------------

 

Spark plug wires. You either crossed up a couple or one or more isn't connected.

Or, possibly a damaged spark plug.

------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet (Holley 3310 on the way), GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

I just posted the same problem a week ago. Heres what I had to do. First I redid the gaskets on the headers because they leaked then I had to get all new spark plug wires because I burnt through 4 of them and I needed a new distributor cap and checked my spark plugs. A basic tune up. Now my car doesn't vibrate at all at Idle where it ued to shake the car violently. Hope this helps. Oh and the headers really do add about 20 horses after everything jells.

------------------
91' red RS convert.
71,000 miles
89' IROC hood
red Z-28 16" rims
potenza re730's
MSD ignition
MSD coil
K&N fiter
350 ported polished heads
hypertech chip
flowmaster 40 series cat-back

 

Did you make sure to install the o2 sensor and connect it properly? When I installed mine, I had to trace it back into the wiring harness and reroute it so it wouldn't burn on the header. Make sure all of the wires are okay and they make good contact with the plugs. Search for loose bolts as well, good luck.

 

OK, I checked plugs, plug wires (bought new ones last night to work with headers), and they were all routed right. No luck, same symptoms. I did notice that the new y-pipe, being bigger, appears to be resting on the "bend" in the oil pan. Could that contact be sending the normal vibrations of the exhaust through the entire car?

------------------

 

Fixed IT!! The driver side header, when tightened, pressed up against the frame, did some mods and they work great! Thanks All!

------------------