Originally Posted by Jayhovah

Make sure you call all of these companies, as some may offer you a small discount as incentive. I have heard this about AAM.. and I believe the same to be true about Gamma.

Also, if price is a heavy concern you need to consider installation costs.
Are you doing your own work?

FI and AAM instruct you to pull the motor.

Gamma kit you install without pulling the motor, but still laborious and not trivial to DIY (though I did.. you can read my build thread for the ups and downs of it).

BP - by far the easiest installation. Commonly done by DIYers. Also the easiest to reverse should you ever want to remove it.