Recently it seems like my car picked up a hick up at around 6000 RPM, when i get that stumble, all you hear is a loud coughing noise from the engine I usually lose power at that point, sometimes I would get power after i past that RPM. It seems like my VDI isnt opening. This only happens from time to time, usually when i want to race.... my plugs and wires are getting old, i am about to change it, do you guys think this is the source of my hick up? My car is a 90 NA. Also what plug wires do you guys recommand

Thanks