Is your blower too small? Maybe it can't supply enough air. Shut the blower off and open your draft door all the way. If the fire picks up, the blower is too small.
2x6 raised flue at a buddies operation from '99-'04
2.5x8 Grimm Lighting at buddies '05-'06 900 taps
Amish built drop flue 2x6 at our own operation since 2007 ~200 taps
2011 - Bought buddies Grimm Lightning 2.5x8 raised flue, 407 taps out as of 2/10/11
Now up to 557 as of 2/27/11
1967 Tucker Sno-Cat 442-A
1976 Thiokol 2100B
I have to be off my rocker