yup , all the old ac's in the high hp left a tell tale track. due to a large injector hole size designed for the maxed out roosa master fuel pump. Moving down to the say "044" tip and yes going to a next size A_R down will clear up the black smoke trail by 'bout 50%... clearing up this smoke was a project on AC dozers in Viet Nam. Noble Harrison (HandR Pittsfield, Ill.) was walking thru the Harvey eng plant and saw two staged turbos on a 2500 on dyno.. He was a avid tractor puller and worked with ED Elgin, a retired AC service rep . The rest is history... his set up on a bunch of tractors won nearly every winter pull incl louisville in '72 I beleive it was.