Thanks for the quick response, Steve. I'm still new at this mechanic stuff, but did learn a lot with the recent overhaul. I just want to clarify what I should be checking.

I have one vacuum line running from the air injection pump to the passenger side firewall into what appears to be a switch of some sort. Another line, which is part of a "Y" tube, comes out of the top of that same switch and goes into a blue and black check valve and then runs the length of the rocker cover (along with the spark plug wires) to the intake side of the engine. I think it is then supposed to plug into the intake manifold, but I'm not sure I have it hooked up right. Back at the passenger side firewall, there is another "switch" just to the left of the previously mentioned one which connects to the other leg of the "Y" tube at the top, causing it to merge with the line that runs over to the intake manifold. Further down on that switch, another vacuum line goes into a black and yellow check valve and then into the EGR valve.

Based on what you said in your post, which way should be air flow in both check valves be going? Where should the vacuum line going over to the intake side connect? I'm not sure about the condition of the two check valves I mentioned. Do they sometimes go bad? The blue/black one seems somewhat restricted and the yellow/black one seems to work intermittently. Not sure if this makes a difference or not.