heads

MP heads are notorious for casting issues which can be seen. But things like seats being out, guides being out of place (like not positioned properly), chamber sizes being all over... they simply are terribly executed. The guys that say they were fine simply lack the tenacity or tooling to check them. RPMs are better done, although they also have guide sizing and sometimes seat and surface finish issues. So any aftermarket head should be gone thru carefully prior to running.