RP is the same on all cyls (the spatial distance gap) but if the "gap" is borderline it can be random missing as different cyls have different charateristics but to KISS, the ans is yes. some of these Q's are redundant but you say capping the hose completely elims the issue? What Dave said, shine your light in there while IDLING & see where RP is at in relation to the cap terminal "bulge with (A) the can capped & (B) with it plumbed into manifold & the can will shift it CCW (SB). I'm assuming you have a dialback, get it running at 2500 & note the (total) timing then plug the hose & twist the dist to get the timing degrees back up to where it was with the can operational. NAPA has a rotor (# MO-3000 iirc) that has a .060" longer blade that helps with phasing ($8.xx out the door iirc) cuz it is the total gap that is in question, the circumferential gap (that you see with the light) & the radial gap (longer rotor helps with that) & if the total gap makes the "required" voltage greater than the "available" voltage from your particular ign setup then it will misfire & the required voltage is greatest at WOT at which point the can is non op (but this is a steady cruise from 2500 on up correct?. Short version: circumferential & radial distance is too great/reluctor gap issue (but we covered that potential)/too much timing (way less likely) but do get a number/cracked cap/bad plug wire(s).