rough acceleration 91 s10 blazer

Hello,
My 91 S10 Blazer with 4.3L TBI "Z" engine has developed a problem.
I have almost 295000 miles on this thing as well.
It has started to have a tough time accelerating under load.
It seems to idle ok at first but then in a little bit the idle speed drops real low.
Acceleration is very rough from idle and the exhuast smells very rich or like gas but does not smoke. I have no codes showing up and I replaced the Fuel filter and removed/cleaned the EGR valve. The EGR valve looked fine to me. The port feeding the PCV valve on the TBI was clogged up. I cleaned the gunk out of it and retried it but the thing is still sick.
And this problem is intermittant also, becuase all of a sudden it will straighten up and run fine.
I have checked for vacuum leaks and cant see or hear any.
I am considering removing the TBI and giving it a good cleaning.
I really am not sure which direction to go here.
And also, the fuel milage on this thing is getting really bad.
I added a can of SEAFOAM to the thing but haven't drove it enough to give a chance to do its thing.
Any suggestions out there as this is my daily driver and I really need it to work right.
Thanks!

What is the engine vacuum readings at idle and at 2K rpm?

I will check them and get back to you on that.
Thanks!

I will check them and get back to you on that.
Thanks!
Also look over the basic tune up end.
Good Ac-Delco plugs?
MT