Ok, so I recently picked up a bone stock 92 GS-R. It sometimes has an issue before 5k. I guess I would describe it as sucking through a straw. Rpms raising slow at full throttle and is very noticeable. Past 5k it clears up and pulls very strong. I replaced the fuel filter. Next one the list is cap, plugs and wires. Any ideas? Timing? Head gasket? Cat or o2?

 

Deff check ignition timing with a gun and reset it to be safe. Check for any codes in the ecu! and a fresh set of plugs might help!