1999 Pontiac Trans Am SLP Performance Parts Test - Trans Slam

It's easy to see how the factory Y-pipe was compromised with restrictive cats and a 2 1/2-inch pipe. The flat (for ground clearance), left-side section of the Y-pipe shrinks to less than 2 inches, causing another reduction in exhaust flow.

There's a drastic size difference between the header and exhaust manifold. The manifold outlet is less than 2 1/2 inches, while the headers 1 3/4-inch tubes merge into a 3-inch collector outlet.

Hank Deniecki is fishing the passenger-side wiring harness through the heat-shield tubing, which is made from heat-resistant fiberglass surrounded by high-temp silicone that is resistant to 1,400 degrees. We added 14 inches of wire to the harnesses' crankshaft sensor, oil-level sensor, and starter-solenoid wires by cutting, splicing, and soldering. However, Hank says that's usually not necessary since there is normally enough slack in the wiring harness.

Ken Estelle lifts the left-side header into place. It may be necessary to remove four of the six K-member bolts (leave the two center bolts threaded in about five turns) and all the bolts to the trans X-member. Prying the rear of the trans towards the passenger side can also aid in squeezing in the headers. Sometimes the steering-column shaft U-joint needs to be disconnected from the steering box for header- installation clearance.

Here's a look at the passenger-side header to the wiring-harness, heat-shield-tubing clearance. It looks tight in this shot, but there's about 1/4 inch of clearance. It's important to install the heat-shield tubing to protect the wiring from frying.

As you can see, the headers are a tight fit, but we didn't experience any interference around them. We didn't forget to reinstall and re-torque the K-member and trans X-member bolts. We popped in SLP's O2-sensor extension harnesses prior to installing the high-flow cats and Y-pipe.