Is your CPP unit under the floor, like original?
Bench bleeding could be the issue--my MC came from a fellow who sells online (Old Irish Dave), and was supposed to have been bench bled already. I didn't attempt any further bleeding, but wonder if there could have been air in the system. When I first put the unit on last year, I had a devil of a time bleeding the brakes, as it seemed there was so much air in the lines. I have considered taking truck to a
"real garage" and asking them to bleed the system with a vacuum pump.
I don't see the issue with the manual trans either, but CPP says that all under floor power brake systems should not be used with a manual trans--the worker that I spoke with there couldn't explain why, but said that I shouldn't buy one.
I've heard nothing but good about CPP, so I'm sure they have some reason.
Thanks for the help!