Could be a seal/gasket leak and the bolts are frozen. Gonna have to get dirty to find out. If you want to put it off a little, you could try adding 5w30 redline HP and a rp 20-820 filter, if that is lifter tick one thing is for sure, that combo at a minimum will change it if not erase it out right. If it sounds the exact same, really confirms it is bolts. No reason to fix exhaust tick, you aint hurting anything, if you feel like verifying it isnt the lifters w/o taking off the valve cover there ya go.