[Wisha Haddan H3]

For HP and torque gains, go with Gibson (not on your list) or Borla. Get the full catback, not just the muffler.

And just my 2 cents, but for any so-called performance products, do not expect better gas mileage. The only way to improve the mpg is to improve combustion efficiency or reduce parasitic losses (friction, air resistance), and airflow products do neither.

Air intake and exhaust mods may allow the engine to breathe better, but that only allows the PCM to add more fuel to accommodate the extra airflow. And it only happens when you ask for it (by pushing the throttle). Since the extra power comes from the extra fuel per engine revolution, you won't see mpg gains.

I highlighted "may" because there are other problems. The question isn't, "Do intake and exhaust mods eliminate restrictions?" You should be asking ...

1.) "Is the stock intake and exhaust more restrictive than the ports and valving in the engine itself?" You won't see any gains unless the answer is yes.

2.) "Did the company engineer the airflow specifically for my vehicle, with regard to the pulse frequency of air traveling through the pipes they designed?" Timing these pulses is critical to pushing air into the intake manifold (or extracting from the exhaust manifold) at the right time.

3.) "Does the aftermarket intake seal off hot engine air?" Hot air is less dense than cold air. In a given volume (like the combustion chamber), cold air will contain more oxygen molecules than hot air. Less oxygen is detected by the MAF, which tells the PCM to send less fuel to each cylinder, resulting in less power from each combustion cycle.

A lot of aftermarked intakes and exhausts actually reduce performance because the company (or kid with the pipe cutter), didn't design the system to your engine application, with these points in mind.