There’s only a few things it could be and it ain’t the springs. Unless someone shimmed the crap out of em and they’re in coil bind. Your retainers could be hitting the valve seals, or the rockers, the valves could be hitting the pistons, you could have junk pushrods that are pole vaulting. All can be fixed relatively easily but you’re going to have to dig in and start measuring and find what it is. Sticking some 906s on ain’t the answer.