re: Manual J - A simple heat load calc was 80K BTU output. (NJ, 2 sty, 2500sq ft w/nominal insulation. Also many windows are still single-pane). Orig 40yo furnace was 120K, guesstimate 65% would equate to 78K BTU.
No static pressure test was conducted.
I won't fault the HVAC friend as I knew of some issues. Also attractive (yeah, shake your heads :-) was the "purchase price value" on this left-over unit plus the rebate. That is why it may be a tad larger than necessary. This one has 95K BTU output and I probably could have gone with their 1600CFM ECM motor. (however there may be governor adjustments on this 2000CFM ECM variable speed motor).
Q1 : Anyone aware of any speed adjustments options ? I know there is a DIP switch setting for AC.
FWIW, I only notice the highest-speed of this "variable" 2 stage blower kick-in AFTER the burners shutdown. (Likely blowing @high-speed to resourcefully dissipate whatever is remaining on the heat exchanger).
I will say, the system (even as temporarily installed) provides much better comfort than the previous unit for the entire 2nd floor. (prior unit never delivered much heat to the 2nd floor).