Poor Gas Mileage

I have a 1993 2wd pickup 22re engine. It's loosing gas mileage. Any suggestions as to what to fix? I've done the basics.

you might want to check your o2 sensor that can be a big prob on these engines they are a bitch to put in uless you have the righht tools

I'm doing exhaust work on my 91 now and found a hole rusted through just before the O2 sensor mount(pre-cat), no wonder my mileage took a dive