When we had a plugged injector, I found results inconclusive when pulling plug wires. Like you, I worried about shock, so only did it with the engine off. What worked was disabling the ignition, running the starter, then pulling plugs to sniff for fuel. Even that I repeated several times before deciding I smelled gas most of the time on all but #1, and never on that one. That was the bad injector.

With our 4, there was a definite loss of power and sluggish acceleration in addition to the lumpy idle. Maybe with the 8 not so noticeable.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7