1987 chevy blazer POS

I picked up a clean 1987 Blazer with a 2.8. Worked fine until about 2 weeks ago. It "hiccupped" on the highway and then set a code 44/lean exhaust code. I changed the O2 sensor and then the TPS because it had a hole in the voltage when you accelerated. I have gone through all the vaccuum lines,replaced some that were iffy. It still hiccupps after downshifting and going up some of the steeper hills here in seattle. By the diagram on the front there is a temp sensor in the air filter housing. One of the ports is going nowhere. No hose on it at all. Im going to replace the fuel filter and the cap this weekend. Is there anything that I am missing or should look at. Im trying to do this my self cuz i cant afford paying the average 90 dollar per hour shop fees here.

Any help is greatly appreciated

You might try putting little rubber caps on all your open vacuum ports and install some new spark plugs. Old plugs don't "light the fire" well.