Streetrod19772000

I have a 1996 Tacoma with a 2.7 with 95,000 miles. In a heated shop on cold start it is perfectly quiet. After two minutes almost to the second it starts rattling like a diesel. I have tried using stethoscope, long screw driver, hose and any thing else you can think of and I cant pin point where the noise is coming from. Just installed new exhaust manifold but that didnt fix it. then after it warms up to point of thermostat opening the rattle goes away almost completely. Can still here a very very faint tick. Any one else having this problem. Thought it could be piston skirts or wrist pins but I just dont know for sure. Eliminated belt noise as I took off all the belts and still makes same noise. I was also thinking balance shaft chain tensioner but why would the noise not be there right away on cold start? Removed valve cover and clearances are perfect. I am baffled. any help would be appreciated. Also eliminated catalytic converter cuz it is dead quiet.