is there a difference in the part number i noticed that the #1 mod has number827509=a7 number 2 and 3 have number 827509=a8 the number 1 cylnder is not firing as strong as 2n3 does any 1 know if there is a reason for this or should i just put on another cdm that matches a8 its a 2002 bigfoot 60 hp serial # is ot624769