Hi. I recently had an ALP150 (AFUE 96) installed, air intake and exhaust piped up the chimney. They did flue gas analysis and the combustion efficiency of 87% seemed rather disappointing. Here are the numbers, from a Wohler A 400

Cal date 9/21/2012

Low fire
O2.....4.2%
CO....4ppm
Effc....87.9%
CO2...9.4%
TS.....148.4F (stack temp)
TA.....64.7F (air temp)
EA....25% (excess air)
SL.....12.1% (stack loss)
Dpt....131.1F (dew point)
COc...5ppm

High Fire
O2.....5.9%
CO....28ppm
Effc....87.4%
CO2...8.5%
TS.....163.4F (stack temp)
TA.....64.7F (air temp)
EA....39% (excess air)
SL.....12.6% (stack loss)
Dpt....127.9F (dew point)
COc...39ppm

Is this the expected efficiency on a condensing boiler w/ AFUE 96? Anything that can be tweaked based on these numbers to improve efficiency? Thanks in advance for your input.