There is also a small stud that secures the heater core coolant tubes to the passenger side of the plenum.
I remove the flanged nut install a un-flanged nut and lock up the flanged nut against it and remove the stud. Then with your hand under the mounting bracket pry the heater tubes away from the plenum and a small aluminum spacer will drop out.
This is a lot easier than removing the tubes to clear the stud when removing the plenum.

And the best part it you have to remove all the plug wires from the coil so you have enough clearance to slip it out! And I don't have SAI to worry about.

I had the same problem with misfires on the same coil.
I wasn't going to mess around swapping them for a test.
I bought 2 new coil packs and replaced them both, saving the good one for a spare.

It's also a lot easier if you remove the hood.
The bottom coil pack mounting bolts are a real pain in the butt and you have to remove them in order to get the coil packs moved back far enough to get the plenum off. I don't bother putting them back in on my rig as the coil mounting bracket is pretty heavy duty. And then you have 2 spare bolts to use when you drop one of the upper one putting them in.

 

Ah forgot about that, too.

I use a Harbor Freight magnet to sort of start the bolts I can't reach and am scared of dropping.