Engine leaning out at 3000rpm

Hello guys it seems my engine has developed a problem now when i mash the gas my engine goes way lean like 16-17:1 pops out the exhaust and makes a hollow kinda bbbbbeeeerrrrrrrrvvvvvvvv sound ive cahanged intake gaskets 3 carbs jetted the thing as big as it can go no change its a 493 with a performer rpm intake 440 source heads checked the vac port for power brakes its good put brand new carb gaskets torqued to 80inlbs it does not idle funny runs good if i keep it under 3000rpm what the heck is going on its driving me crazy im switching to a single plane intake this weekend got the expensive hughes engines intake gaskets and a new pan and some hylomar blue so im gonna seal the crap out of it hopefully last time i took the intake off i had a little oil i the intake runners of the heads and oil in the intake bolt holes is my engine sucking air from the valley? Any help would be appreciated