Hello all,

So, I have decided on replacing my stock '05 (man6) exhaust (there is a axle back Corsa in place) with SLP long tube headers, high flow cats, and power flo x-pipe set up. What can I expect to modify, or replace in the engine compartment. Basically, things like, needing to upgrade air filter system. My first headers on a late model, so not sure what adding headers might require for engine wise.

 

Your stock air filter set up is fine, so long as the filters are clean. If you don't want to lose HP as the hood area gets hot from sitting at a stop light too long and the car start so suck in the much hotter air before you start moving to lower the air temp in the hood area, then a CAI will help to minimize that. Hence as the motor draws in hotter air, it cause the timing to be retarded as well.
Note, CIA has to pull air from the outside of the hood air, and even just propping the shroud open with the stock filters will help that; without out having to change a thing. Speaking of filters, tend to favor the napa Gold filters. Not because they will flow better than the stock one, but since they are white'ish and I can tell when they are getting dirty and need to be changed isntead.

Chart on air temps and how much timing the motor will pull with a stock tune.
Attachment 48334173

As for with the headers and high flow cats installed, you will need to have the car tuned. The headers will allow more air flow through the engine, which in turn makes the car run lean instead. Also, since the high flow cats are moved rearward off the engine heads area, they are less efficient, meaning that the rear O2 sensors will be deleted, and will need to be tuned out in the tune.
Short version here, the pre cat O2 sensors are used for the motor to adjust itself AFR in closed loop (WOT the car goes into open loop, and it all tune alone that is controling that), while the back O2 sensor after the cars are just there to make sure that the cats are working correctly only. So with the stock cats, there is enough differential reading that the car is happy. High flow cats that have been moved back, not enough differential reading and the car starts throwing codes for the cats isntead.


As for before the tune, not only do you want to make sure that the air filters are clean, but take the time to clean the MAF as well.
Note, when the car is tuned, the hood will be open with a fan blowing air into the hood area. So even if you did install a CIA system before the tune, they are not going to show up in the resorts.

Now having said that, and the fact that some CAI system really screw up the clean readings of the MAF sensor since they can cause turborlance through them, if you are going to install some after market CAI system, do so before its tuned. This way the tuner can adjust for the irregular MAF readings as he is doing the tune.

As for HP gains (will come all from the headers alone from what you have listed), your looking at about a 25 to 35HP gain. If the car has not been tuned before, it's going to be a huge night and day difference. Not from the 30'ish HP that you are gaining from just the headers, but the fact that in stock form, the TM is holding back a lot of instant power instead. Even in stock form with just a tune, seat of pants peformace feel gains are huge once the TM had been de-hobbled.

So your LS-2 is putting out ASE 411HP if still fresh stock. Tune alone on the stock motor bumps that HP to 426'ish. With headers added on during the tune, then should be slightly over the 450Hp mark with the tune, and maybe close to 460 depending on the engine and what the tuner can get out of the motor extra. If your tuner is really good and can adjust the timing and ARF in open loop so the motor will pull hard to/ slam off red line, then should be in the 465hp+ range (maybe, and all depends of the mess that Oem intake manifold is, and how much its holding you back.

As for the stock LS-2 intake manifold, ported and polished will gain you around 10hp with the stock cam and headers at red line. By going to say a fast 102 that has been ported, your still close to the same 10hp gains over all at red line, but with the Fast cleaned 102, what you pick up in the meat of the RPM;s over even a ported oem manifold is huge. So headers, tune, and ported fast 102, your tuner should be able to get you close to 470~475HP at the crank instead.

And again, CAI system is not going to show up as a HP increase in the tune, since the car is dyno'd with the hood open and fan blowing into the engine bay to keep the engine from over heating. Hence the stock air filter system already over flows what the engine needs (even with headers) and it's not until you go to wild mods with a cam that you can get even close to requiring more air that the stock filters can cleanly flow. So it not the increase flow of the CAI that makes a dam on the stock motor, but that it will pull cooler air in from the out side of the car, keeping the motor from pulling timing as it sucks in hot air instead.

 

To add, why headers increase HP, hence scavenging.