prob w/ skipping @3k rpm in 96 Montero SR

[ck from ga]

looking at buying a 96 Montero SR. owner says that when he gets up to about 3000 rpm, engine will stutter and skip. lets off accelerator,problem goes away, may or may not come back when accelorator pressed again. had plugs, plug wires, distributor, rotor, coil, etc. changed to the tune of about $3600. last time at shop was told it was caused because he needed valve job ($1200). he's fed up, selling truck, asking $2000 OBO.

My question, could needing a valve job cause that or did he get his chain pulled. If not valves then what? computor?

trucks in good shape otherwise, looking for reliable vehicle for daughter.

thanks,