I have two unit mowers ,the same built, but different engines,same hp! One is a 18hp vanguard,the other is kohler chs18. when running both the vanguard and kohler.vanguard at full throttle, kohler about 3/4 throttle are (in-sink or in tune) with one another! the kohler sounds good at full throttle and sounds like 3600 rpm with no load. the vanguard does not match the kohler rpm. can I tune the vanguard rpm to the kohler which sounds good! I have no rpm tack. Can this done by the governor bracket control on the briggs or the Gov control lever adjustments? or take to the shop? thanks for any idea's!!