Thanks Dave & Richard.... Richard is right...I've calculated the pressure correction factor for SIF to be 1.23078...I now get the right SIF upon dividing my calculated value above to this pressure correction factor...That is:

SIFin=3.225/1.23078 ~ 2.6
SIFout=2.687/1.23078 ~ 2.18

I was thinking that note is for D/T > 100 (thin-walled elbows), but my interpretation is incorrect because D/T value is not specified in that note. The D/T in this case is (16/.375=43) which is a little bit higher than 40. From the previous webinar of Tony Paulin, he cited this rule of thumb for D/T greater than 40 as something to watch for in performing stress analysis.

Anyway my mind is now clear from the SIF calculation as per Appendix D of B31.3 for bends & elbows..

Cheers!!!