1999 Pontiac Trans Am - 5 Performance Modifications - Take The Money &Run

For those LS1 owners not blessed with the stellar LS6 manifold, there is the EGR mod. The tube that enters on top of the composite manifold hangs down into the air stream, but a quick chop to the EGR tube's manhood will remove this obvious obstruction right after the throttle body.

The EGR modification is done by removing the 10mm bolt holding the tube into the manifold. Once the tube is out and the O-ring is removed, cut the tube right below the hat mount ridge with a die grinder or a cutoff wheel. Be advised: if you cut the hat mount, the hat will fall off and there will be no way to remount it.

Once the cut has been made, use any file to de-burr the shortened tube before reinstalling it with the O-ring and the bolt.

Bypassing the throttle body coolant line came next. In this photo with the throttle body off, the rubber line that goes from the radiator to the TB is seen on the left, with the metal line connection that takes the TB's rubber hose on the right.

We were also curious to see if any of this skullduggery would have an effect on the air/fuel ratio. But all porting, grinding, and screen removing aside, our before and after air/fuel numbers were almost identical.

The factory hose coming off of the radiator outlet is unhooked and discarded.

A 5/16-inch hose will be used for the bypass to connect the radiator outlet directly to the flow crossover tube, and regular worm clamps are preferred over the factory clamps to get the line nice and tight.

Another spin on SLP's dyno answered that question. From a baseline of 292.2 horses and 299.0 lb-ft of torque, five free mods bumped the '99 T/A's power to 302.3, with 306.6 lb-ft showing at the rollers. That's a whopping 10.1 horsepower and 7.6 lb-ft for free!