First: where are you attaching your vacuum line?
You want it after the throttle body
Second: real long hoses between the vacuum gauge and the intake can affect readings.
Third: do the test with engine cold and engine fully warmed up.
that way if you have a vacuum issue that is only present when cold or hot you have a better chance of seeing it.
fourth: When you do the test start by just letting the engine idle steadily.
Just watch the gauge for 2-3 minutes at idle. watch for needle action if any and note the reading.
ideally you want a rock steady needle. at 18-22 in.hg
Fifth: do a snap throttle test: from Idle go wide open throttle and quickly release the throttle. Needle should very quickly drop to near 0 then rebound to a little over idle vacuum reading then settle at idle reading.
Let the engine idle again for a few minutes and see if readings vary from the first idle session.
The dark plugs appear to be oil fouled or a very rich fuel mixture.
You have replaced your coils more then once so they are most likely good.
Don't switch them around. If there is a misfire issue related to coils or plugs your just moving the problem around.
We want to pin the problem down.
Test them in place under running conditions. Use a spark tester that goes between the plug and coil. they light up every time the coil fires the plug.
Or use a digital volt meter.
or do it old school by pulling the plug hook it to the coil then lay it on the head and crank the motor look and see i the plug sparks.
If you are positive that you have misfires on bank 2 then we need to concentrate on bank 2
Test the coils on bank 2 in place on bank 2 that way we know if the wiring to the coils is good or not.
The oddest thing to me about your problem is: if you are having misfires but you have no CEL or codes something is not right with the DME/ECU or the wiring.
Or something is not hooked up right when the engine was replaced.
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