Sealing hole in concrete outside?

25.5' is what I added up. You should still be fine because it's 4" vent.
Not counting the 45° vent angle because it's the last piece. Even with that, it's 28'.

Good to go

 

Lazy flame, Sooty burn(mostly on low fire).

I've had no issues with 4" and 28+ EVL. And my blower aint got the power yours does. I had to increase the blower speed one notch on low burn is all I saw for draw backs.

 

I wish I would have rotated mine.

The distribution blower should be cleaned/brushed/blown out every year (or every other year at most if you run a filter constantly)

The combustion blower should be removed yearly (old style like Mike and several others) as well if your burning 3-4+ ton. The new units have the clean out plate like yours.

I also clean and blow out the 2 channels that the distribution blower blows through (50% goes through the heat exchange tunes, the other 50% blows under the bottom of the furnace and comes out at the little slot by the bottom of the door). Just a quick hit with my little brush and blow some compressed air through there.