Makes no difference..

The idea is to block the vac line so that when the delay shift is activated by the ECU, the leaking element at the trany does not allow air to be sucked into the engine intake while the shift SOV is OPEN..that's all.
That could be your vac leak..by plugging that line anywhere before the trans cable element , you have eliminated that possibility.
I am fairly confident from what you have posted that your vac line from the SOV down to the tranny will not hold a vac..[you can test that with a hand pump..] If it doesn't , then you know the VERY common problem of a leaking/split shift actuator elment is the problem for code 26.
You went and changed the shift SOV, when you should have tested the green line going from the SOV to the trans actuator for vac holding.

But that may/may not not be what is causing your limit stop @ idle .
So, the simple test is to get rid of that possible w/BB

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A Dalton