Suzuki samurai has no power

I recently acquired an '86 suzuki samurai from my stepdad. the engine (not the original) has 17,000 miles, and starts and runs really well. I press the gas pedal, and the RPMs increase accordingly. But, when I put it in gear and try to start driving/put any load on the engine, the engine dies. I am an experienced manual transmission driver, and i’m not just killing it. I’m thinking it might be something stuck in the carb, or something to do with the complicated emissions system. Any ideas???