Olddog,
Leaks are ALWAYS a pain and frustration...!
I doubt it was the RTV.
The gaskets, compostion, what ever are pretty solid compared to RTV.
The RTV comes out of the tube pliant...liquid to gel...seems unless the assembler waited for the RTV to pertify, it will squeeze out before the gasket.
I have aluminum heads, iron block.
My intake manifold gaskets failed after 3000 miles...it was I think due to not re-torgueing the intake bolts.
The gaskets...Fel-Pro super something or other...looked like tortured snakes around the ports...but the RTV BEADS at the front, rear, and around the water ports looked to be fine.
Now, how could a semi-liquid-gel-paste RTV could support the manifold higher than the composite gaskets under 22 ft/lbs of torque?
After I replaced the gaskets at 3000 miles, 500 miles later I had a rear manifold
oil leak...because I did NOT use ENOUGH RTV to get a solid bead across the rear of the manifold/block interface.
Now, I do re-torque the intake every
oil change or so...more often actually...Have 10,000 more miles since the LAST gasket change and no leaks.
Intake gaskets for me have proved to require re-torquing...often.
Pete