I don’t remember when the problem started, truck has been garaged for about 5 years and I’m bringing it back to life. I just remember the brakes were super sketchy. The proportioning valve was new but I’m not sure if the problem started after I swapped it. I’m just wondering if I put the wrong one in. When I get it running I’ll try the booster check. I’ve never diagnosed a bad booster. I remember the pedal being like a rock at slow speed where I had to stand on it. At faster speeds if I pressed to hard the rear would lock up, fun as hell but dangerous. I was going to buy a whole new master/booster/valve from classic industries but i would rather not blow all that money if I don’t have to. I’ll try to post a pic. Thank you