i have a 2001 chevy tahoe 5.3 i have a PO300 code random misfire ive changed the plugs with ac-delco iridium plugs bosh wires same problem a mechanic told me its probably a coil i have 8 coils how do you know which one is bad how do i check them

 

Can you feel the misfire? When does it do it? idle or acceleration?
Generally when a coil it bad it will set a cylinder specific code like PO301 -308 the last number being the specific cylinder.

 

all of the coils are firing theres only a po300 code no specific coil its just random misfire on the meter

 

what are the chance's that its a intake manifold gasket