Tore one out recently (replaced with TCI X6). Was trouble-free, was a "built" (Stage 3) version, a bit over 600HP. I do think that was about the max. that tranny (4L60e) can handle in long-term street use. Most amazing part was having a real hi-stall converter that still locked up solid...kinda like having your cake...

Much more responsive shifts than 518 - no bands, no super-long fluid paths to "added on" overdrive.

Was kinda close to TTI headers and X-pipe, but later TTIs have been redesigned around the tranny.

Easy install. Fun to program. TCI's software / controller basically identical, now I'm an expert(?)

Rick