got a dc2 type r teggy, after i give it a good thrashing it sort of ruts when it gets down to 800 revs, on the rev meter on dash the needele stays @ around 900 but on my vafc2 it jumps up and down from 780 to 820 revs, is this just a case of replacing the inlet manifold gasket? and what spark plugs do i use? it has after market cams, cam gears and flows and full exaust, ive just been using ngk normal 1s for last 20thou ks but they need replacing, are iridiums any good? any 1 can help??