when im using full throttle above 4000 rpm the car will pop n bang a few times from the exhaust with each pop comes hesitation if i use say 85% throttle it doesnt happen the car is a 93 jdm with sti engine about 330 hp any ideas what this could be

 

coil packs probably.. they start to break down over time.

try removing them and remove the rubber end cap and check for cracks.. also remove the plugs and check the plug gaps are around 0.7~0.65mm... also worth replacing the plugs if a bit old.

Simon