Could you have moved the pickup during the cap change? check your reluctor gap and reluctor ribs. Are you missing a vacuum line somewhere? Might want to bump the motor with the valve cover off and see if the #5 valves are moving.
X2 :cheers:, could be a bent push rod, This is a newer /. :tard: Could be a bad lifter and not pumping up.. I agree pishta, remove the valve cover and see if #5 is rocking as much as the others :D sorry..