Need Help With This one

[dapper15]

I bought a 94 Mazda B4000 that had a blown engine. I found a 94 Ford Explorer engine for the truck. After installing the engine and getting everything all hooked up again I have a problem. The engine is idling rough, so I replaced the coil, plugs, etc. Still idling rough, but thats not the big problem. It holds idle right around 600 rpm's, and I can run the engine up without a problem, until I put a load on it. When I put a load on it the truck falters and wants to stall out, but then Ill release the gas, the rpms will go up a little bit and then go back to idle. My thought was the fuel filter, seems to be logical, changed it out, but it is still doing the same thing. Any ideas? The truck was sitting for 9 months and the guy before me never put stabilizer in it? Any ideas would be helpful. Thanks

[jasonl]

Did you do a compression check on the engine to make sure it is good or hear it run etc? Could be bad gas if it sat that long.