Occasionally on my 182k mile '93 1.6 I'll get this weird hiccup when accelerating. Usually it happens just as I'm bringing the revs up and starting to engage the clutch so it doesn't affect driveability. (yet) My concern is that it will get worse though. My car is normally aspirated, with a racing beat header, magnaflow cat and 2.5 generic stainless exhaust. I've got fresh Ngk standard plugs, new-ish coil pack and Nology wires. Cleaning the throttle body and performing a seafoam treatment have done nothing to alleviate the condition. Any thoughts?