The Dynatech header kits come with a provision for the EGR fittings used in the '00 model cars. There's a small, brass pipe plug in the center of the header's EGR flange that has to be removed and dumped for the '00 cars. The plug remains in place on all other model years.
We slipped individual headers into the engine bay from the bottom of the vehicle and had a helper slide the kit-supplied gaskets into place and start a couple of the bolts on each after giving the threads a little dab of antiseize. Make sure your helper sets the proper gasket orientation, because getting it wrong at this point will create clearance issues with the spark plugs. We cinched all the bolts to 18 lb-ft and then reinstalled the spark plugs on the driver side.
Next we lowered the car and reassembled everything we disconnected under the hood. Once that task was complete, we moved back under the car and removed the factory exhaust hanger bracket from the transmission and put it into the parts box with the rest of the stock system. It won't be reused and there's no need to leave it hanging there.
The next step was to slip the two 3-inch doughnut gaskets over the end of each collector, making sure the flat side of the doughnut was pushed tight against the collector stop ring. The two PowerCAT converters were lightly bolted into position at the ends of the collectors.
We put a new clamp on the Dynatech Y-pipe and slipped it into the inlet of the stock tailpipe. We grabbed the passenger-side exhaust tube and slipped it into the converter and Y-pipe, repeating the procedure for the driver side.
Now that everything was in place, we swung the sheetmetal crossbrace back into position and secured it using the factory bolts. Kit-supplied band clamps were then positioned over all the joints in the new system and snugged. Working from the rear of the car forward, all the clamps were tightened, making sure the new pipes didn't interfere with any underbody components. We applied a tiny dab of antiseize compound to the threads of all four oxygen sensors and installed them into the new system. The rear sensors were fitted with the new pigtails included in the kit. We used the kit-supplied tie-wraps to secure the sensor leads away from the headers and clear of all the moving parts.
We checked the installation to make sure we didn't miss anything and then fired up the car to check for leaks. We also checked to make sure the "check engine" light didn't come on. Dynatech said some models will record a slow heat response or temperature error that will set off the "check engine" light. The company said this has no adverse effect on the operation or performance of the engine, but it can be annoying.A quick tweak of the ECU parameters with software such as LS-1 Edit or similar can shut off the light for good.
After making sure we were leak-free and weren't getting any untoward illumination on the dash, we jumped in and drove back to Willy's Carb & Dyno Shop to see what kind of improvement the new header system gave the Pontiac. We strapped the car to the dyno and made a few pulls. The addition of the Dynatech system racked up 348 peak rear-wheel horsepower at 5,700 rpm and 359 lb-ft of torque at 4,300 rpm, an increase of more than 20 rwhp and 13 lb-ft of torque.