So I tore into the intake over the holiday weekend. The weather has warmed considerably, so it is difficult to say if anything is changed.
The gasket I got had a raised center bolt portion that the OEM gasket did not... I am not sure why, as it doesn't fit into either the intake bolt hole or the block. I ended up having to cut the raised portion off and file it down. It should not affect function, as it is just the bolt hole and the port openings were fine. I posted pics of the gasket below.
Things I found:
First, my injectors were completely filthy, all gummed up around the tips, some had debris on the actual spray area - but most were just gummed up all around the tip. I cleaned with gasoline, the seals seemed in great shape. I did notice, that the excess fuel that came out of the rail while I was cleaning the injectors, was black colored. I have a new fuel filter, so not sure what that is about, maybe just residue inside the rail.
Second, the gaskets between the plastic and metal part of the manifold were separate units that had little squares (photo below). These all seemed to be in good condition, and appeared to be designed to almost allow some air passage?? Thought that was weird. These little square areas along the intake's seam is where the carb cleaner was making the engine change idle pattern.
Third, my actual ports down into the block are caked full of carbon build up, I am not sure what type of buildup to expect @ 150K miles, but it seemed excessive. I did my best to clear some of the gunk, but was afraid to get loosened pieces down into the engine - so I did not do any extensive cleaning.
Also I forgot to put back in one of the little brown insulation/sound dampening pieces that was somewhere sitting on top of the block... But it was all beat up and seemed useless.
Old gasket next to new gasket.
Little gaskets between plastic and metal part of intake.
Build up in the engine:
