hi, i've just recently picked up a series II r33. i've noticed that sometimes when i boot it, it has a really slight stumble at about 4000rpm, then at about 5500rpm. its only very slight but you can feel its not revving freely through the range. sometimes it doesn't do it though.
i was thinking spark plugs but what do you guys think
its got standard ecu, hks filter in the standard box, 3 inch cat back but running standard cat for compliance (haven't got around to changing it) oh and running standard boost.