I have an ALL STOCK 305 TPI, T5. N10 80,000 miles.

I put the 52mm Holley Avenger on it, and no matter what anyone says, there is a SOTP difference.

I know, there are 10 zillion nay-sayers that says it's a waste of money. But the difference is there. Crisper throttle. feels stronger, etc, etc, etc.

 

Ok,now head to the dyno and make us care.....

 

Send me $300, and I'll run over to a dyno with both TB's.

 

There should be a little bit of a difference but not much - especially on a stock LB9 305 motor.

GM designed TPI and optimized it for the 305 motor to begin with so even though a factory stock GM long tube runner TPI system has it's limitations they are not as much as a hinderance to performance as they are on the L98 350's and larger cubic inch motors.

To see really good measurable gains the entire system that you are dealing with needs to be upgraded & the components must all be matched.

For example installing a performance muffler is a good addition but if the rest of the exhaust system is stock you won't feel too much of a gain. On the other hand if you install a high flow cat and full aftermarket cat back exhaust that has mandrel bent pipes you will see and feel more of a measurable gain in power.

With the intake setup on TPI cars a lot of stuff needs to be done to really open it up. Start off with building your own cold air intake system and some high flow aftermarket air filters. I don't know if you have a Camaro or Firebird.

I've got an IROC Camaro and I started modifying my factory intake by gutting the air boxes and cutting out all the baffles so that there is nothing beneath them. Then I installed some K&N airfilters. I bought some Hawks Ram air boxes and screwed them to the bottom of the gutted factory airbox. This set up works great because this is a properly working ram air system now. The air comes past the fog lights and is funnled right up to the filters with no restrictions.

The Firebirds are different and would benefit from a cold air intake kit simular to what SLP used to sell. I wish that company would still make products for thirdgens.

Then in addition to the larger throttle body install an aftermarket set of intake runners, a base, and have them port matched to the plenum. This will give you some real gains on the intake side with a large tube runner TPI system.

Since you have got the dual cat factory exhaust set up you have the highest flowing factory exhaust system. Having said that some headers, matching y-pipe, dual high flow aftermarket cats, and the after cat exhaust system of your choice would really help out the performance especially when the intake mods were done.

The exhaust (system after the cat) on the L98 cars and LB9 cars with the L98 cam have a descent exhaust system from the factory compaired to cars that didn't get the highest factory performing exhaust systems to start with like the L03 305 TBI cars did.

The headers and y-pipes really do restrict exhaust flow on these cars and that is why you will really gain a lot of performance when you upgrade your headers and y-pipe.