Welp... after weeks of struggling with this kit (need to modify the axle, a completely bogus caliper that had to be replaced, need to grind the rear calipers to clear 15" wheels, which shouldn't be needed), my mechanic is telling me that the whole system is very "spongy"... pedal needs to mash to the floor just to grab. He says pressure is good, master cylinder is good, and tells me another customer with a similar Right Stuff kit had the same problem. His opinion is that Right Stuff is just garbage and I should toss it all in favor of something else. Now I've become used to the fact that I'll often have to light thousands of dollars on fire in order to get classic cars working, but just chucking a $1500 kit like that is giving me pause. This shop is VERY highly rated and did expert work on other parts of my car, so I'm hesitant to mark it up to the incompetance of the mechanic, but if that is the case, perhaps they would have an equal lack of success with another $1500 kit. What the hell do I do now?
Did you speak with or email a tech at Right Stuff or even Summit? I would do this first before throwing in the towel.
I have never used their stuff so I can't really give an opinion if good or bad. However, something sounds amiss. Looking at the Summit photo, if accurate, I see a threaded rod coming out of the booster. Don't know what this adjusts on to, a heim joint? Maybe the length is incorrect for your application? Did your mechanic compare the original length of the rod that was in there to the Right Stuff rod?
Pontiac pedals typically have 2 holes for mounting the brake rod to master cylinder. One is for the manual non-power brakes and the other hole is for power brakes. Is the rod mounted in the correct hole position?
Now spongy would tell me that something is wrong within the system whether is be air, incorrect brake adjustment, vacuum/booster issue.
In my opinion, I think you have 2 different problems going on. Again, I would not throw in the towel and get frustrated enough to throw your money away and invest again in another system. These companies, both Right Stuff and Summit who promotes/sells the product, don't want unhappy or disappointed customers because negative reviews travel far and fast. So I would consult with them and it may be something very simple or even a brand new defective part that needs to be swapped out.