I recently traded my wife's '03 Diamante to a longtime friend for his helping us get tile work done in our house. He got it for his daughter.

I live in CA and of course there's smog laws here. I rebuilt this engine a few thousand miles back because a lock washer that someone who previously worked on the car must have lost the OEM integrated nut/ washer on one end of the intake manifold I later realized.
Well, not knowing it was even there, as I lifted the manifold off to change the rear bank plugs and wires, it quietly fell into intake hole number 6, sitting down there, wide open like a baby bird's mouth waiting for a worm.

I went about doing my tune up work having no idea that this even happened. I used 2" blue tape to cover that series of holes while I worked, not knowing the enemy had already invaded the camp I just put a safety perimeter around. lol.

Well, the only way I knew there was even ANY problem was when I cranked it to start it after the "tune up". There was that halting cranking you get like when you have a plug wire out of order and that's all I thought it was. So, I cranked it more to at least start it and then identify which cylinder was switched...not knowing that wasn't the case!

may have to continue in another thread....don't know how wordy you can be and I can be wordy...lol.