sounds like u might have u'r cam-to-crank timing off, if it sucks in on the exhuast then blows out. do that test on the intake side too and see if u get the same result. if u do, then that's definitely u'r problem. a timing light will tell u if u'r ignition timing is off base w/ the flywheel. but it won't tell u if the cam is off time w/ the flywheel, since u can adjust the ignition timing indepentantly of the cam. if u changed the timing belt, or it was changed before u got it, then i'd double check that to see if that's the case. it could be off a tooth or two and that has been the problem of someone else here in these forums