2.3L ('83-'97) Running lean?

[Treefarmer96]

The truck idles ok for a few minutes if you just pat the gas lightly it will rev but if you give it much it either stalls or starts backfiring through the intake. I’ve replaced the fuel filter and the truck supposedly has new plugs and wires. I haven’t found any vacuum leaks and the MAF has a little crud but doesn’t look too bad. Previous owner did some funky things with the wiring to the fuel pump could that possibly be the cause? I also noticed there is a broken tube that goes from the exhaust manifold to below the air filter box and I have no idea what purpose it served. Thanks for any advice in advance!

 

[Dirtman]

"MAF has a little crud but doesn't look too bad."

No amount of crud is OK for a MAF sensor...

The tube from the exhaust manifold to the airbox was a air intake pre heater. Used to help cold weather starts. Has no effect on how the engine runs.

 

[scotts90ranger]

Yeah, that...

Running steady state at idle it can fix things with the oxygen sensor, but get it back to looking at the tables based on engine speed and airflow where the oxygen sensor learn table hasn't learned it will run bad...