ZX2 sluggish power

I'm looking at purchasing a 2001 ZX2 sport with 80K. The car is available for a real decent price ($700). The seller mentioned potential engine issues. During a test drive, I noted very sluggish engine performance (my son has a ZX2 with 138K that has almost twice the acceleration). At freeway speeds or driving uphill, with the accelerator pegged, the engine will occasionally start to buck. Let up on the gas momentarily and the bucking goes away. The check engine light is not on, and other then the bucking, the engine runs smooth while idling or driving and sounds fine. Everything seems normal except for the sluggish power. The seller said the problem started 4 months ago and hasn't gotten any worse. Any suggestions on troubleshooting? PCM issue? Compression? If the engine is on it's way out, even $700 is not attractive to me.

Check the condition of the plug wires and spark plugs. That can cause that symptom. I'm not sure, but poor compression on a cylinder might cause that too, and that's a more serious issue.