Your not going to see large gains at peak but it does bring 8 hp to rw...But throughout the powerband it helps alot. Worth the $ I love mine...The options and diagnostics alone are great !
A/F ratio, timing, rev limiter, top speed limiter, automatic shift points and firmness, adjust speedo for tire sizes and gear changes, Idle rpms, turn O2 sensors off, and turn Traction Control off... and other stuff, like data logging and its also a code reader.
I had to send my tune off to RWTD to get it right. My car was running WAY to lean. I had to se it to 40% richer to get it to run right. Cool thing about the Pred. is that you can download your stock tune to a PC, then e-mail it to a tuner. Then when he is done with the tune he can send it back to you, and you just load it onto the Pred. If you have the comp code TMX2 be careful about the stock Diablo tune.