We have a PowerPack and Transcommand on our ‘99 30’ V10. They made a very noticeable improvement in power, hill climbing, better shifting (less hunting and more “crisp” shifts), and the engine runs much cooler. We felt it was worth it, even if it WAS expensive, for the secure passing and hill climbing ability.
Our fuel economy went down ever so slightly (probably not significantly) and probably due to more assertive acceleration - taking advantage of the extra power. We definitely don’t even notice our Saturn SL2 toad.
The stock air filter was replaced with an K&N filter for better filtration and improved airflow.
Here is what the exhaust headers look like, this is the set on the driver’s side; the improved exhaust is the heart of the Banks system.
The massive tailpipe attached to the equally massive exhaust pipe tied to the headers.