I fitted a PFR pipe onto my YZ125G, went on like a glove, NP's.
Recently put a DG onto my 82 CR250 & not a good experience. After several hours of juggling, twisting & doing my head in, had to fit the exhaust manifold into the pipe before going onto the bike & then really struggled to squeeze it on. Even then, the pipe is now hard up against the frame & probably need to do something about that