I recently got an email from a friend that installed Dyntech MuscleMaxx 1 3/4-1 7/8 step headers on his 401 sbc,HE WAS USING HEDMAN 1 3/4 HEADERS:....Boy, did it make a difference! At SIR in Tucson, picked up .270 with about the same air as we had when I ran down there in March! Went to Firebird on Monday for a little test session and with air at about 1150' went 10.051 at 131.96. I think that is the fastest this car has been. I know the 60' was my best ever at 1.370 in this 3165 lb. slug with the small block 401 in it! EGT's were 1320 - 1352! Went up 2 jet sizes as I don't like being that close to lean!