-94 GP 3100 misfire

[Mike1972]

It seems like my engine is misfiring.
Everything is fine at idle but under load it´s like it clogging and doesn´t respond to gas.
The thing is that on a dry day there´s almost no problems, but when it´s raining or a lot of moisture in the air the car is almost impossible to drive.
I´ve checked the codes, the SES sometimes lights up but not at the same time as the misfiring, and it reads a code 13 and 44. (O2 circurit?)
I´ve changed sparkplugs and wires, no change.

Hope someone can help me!

[dwalmop]

The 13 is the o2 circuit, and 44 means simply, lean exhaust. Check for vacuum leaks. It's even possible you may have the dreaded lower intake manifold gasket leak. good luck.