TPI Tricks
The knock module in stock LT1's is too sensitive and is subject to picking up "false knock." The computer thinks it is picking up knock and it retards the timing, sometimes up to 22 degrees. This results in serious loss of performance. False knock has been reported most at high rpm's by many types of monitoring devices. Vibration, and valvetrain noise are attributed to the false knock. The best way to help this situation is to install an LT4 knock module ($30). It does a better job of interpreting knock sensor signals than the LT1 module and it weeds out engine noise. Some people say they don't notice any difference and some are very impressed, it just depends how bad the problem is in the first place in your car. For the price, I highly recommend it. Knock sensors are rumored to be overtightened from the factory and thus be oversensitive. Back it out, but not too much as to drain coolant, use teflon paste and torque it at around 14ft-lbs. The car will pull significantly harder from 4800-6000rpm. You will no longer feel as much lost power when the engine is hot and the weather is hot and humid. Premium fuel recommended. Don't even bother with this though if you have the new knock module. Click the link above for directions and more info on the LT4 Knock Module.
Wiring in resistors to create this circuit will desensitize the sensor by 25%, which is more than enough to clear false knock. Any more would be stupid since it is there to protect your engine. If false knock retard is a severe problem in you engine, you should find the cause first. This was originally used for an LS1 that had 25+ advance, the known cause was exhaust pipes rattling and simulating detonation. Whoa!
Relocated IAT (Idle Air Temp.) Sensor
The stock position of the IAT sensor (in the rubber intake elbow just before the throttle body -on an LT1) causes it to pick up a lot of intake manifold heat (10 deg. at highway speeds/30 deg. at idle). This causes the computer to retard the timing and run the engine too rich. Moving the sensor away from the manifold will give more accurate temp. reading and the computer can properly adjust the ratios/timing. The stock hole must be plugged and you can relocate the sensor to the airbox. I've heard a cool trick is to mount the sensor in the washer reservoir where it is much cooler, but I would research that more before doing it. Either way, the gains are very minimal, but it doesn't cost anything.
EGR Valve Bypass (LT1)
The EGR re-routs some of the exhaust gases back into the intake/combustion chamber. This is done to reduce emissions. Blocking it off will lower the temp of the intake since the gases fed through the EGR are very hot. Lower intake temps produce more power, but the amount of gases going through the EGR are minimal and probably won't result in much of a gain (if any). If you look at the back of the passenger side of the manifold, you will see a tube that runs up to the intake manifold from the exhaust manifold. Take the tube off, pull it back, and look at it. You will see a two bolt pattern with a hole in the middle. Make some kind of plate to block the hole, guided on the bolt pattern. You can make the plate out of a piece of scrap metal. Re mount the tube with the plate in place. Do it cleanly so it will pass a cops visual inspection. Note that the plate will have to be removed for smog inspection, since the recycled exhaust gases reduce emissions.
Mass Air Flow Sensor Screen Removal
If your TPI is equipped with a Mass Air Flow Sensor, it has screens on each side of the sensor on the intake tubing. Remove the section containing the sensor and cut the rubber at the edges just enough to remove the screens. This will improve flow capacity and is a quick and easy trick to do.
This mod is done because the engine can't receive the full gain of the cold air intake and other mods because of the restriction of the MAF. Get out a saw and a grinder and port it up nicely. The results are amazing! Pulls MUCH harder across the rpm band. Once you take off the screen, look inside. Past the sensor wire, you will see a sort of divider wing thingy, carefully cut it out and polish it nicely. I have to tell you though, this mod has been known to drive the computer haywire and actually make the car SLOWER! The results vary greatly so I would HIGHLY recommend researching this before doing it. Click the link above for step by step instructionson performing this mod on an LS1.
Coolant is run thru the throttle body in order to keep things from freezing up in extreme cold weather conditions. If you are like most of us who don't live in these conditions, then your performance is suffering from the Throttle Body "Warming" Line. When hot coolant is pumped thru, the TB is heated and so is the incoming air, making it less dense and creating less hp. Click the link above for a diagram and directions on re-routing the coolant.
This mod will allow for pressure adjusting without buying an aftermarket regulator. Haven't tried it myself but the above link will give instructions.
If you look into the TB, you can see how far down the valve sticks into the air passage hindering flow. Trimming it cleanly will improve airflow. The results are not noticeable but every little thing adds up right? Don't trim it flush though, leave a bit protruding into the TB or else air will not flow well into the EGR and you may get a trouble code.