own a 7000w twin cylinder 14 hp.,replaced original muffler by a large Onan one916"x8"x3 1/2" oval with a stainless steel flexible.Plan to mount on a small trailer with enclosure on top and sides with generous room for cold air pick up.Intalled an electric blower at the back,One side of the dual blower is really blowing at lot of hot air even without the enclosure.Does not seem different under a 4000w test load. Could the muffler produce to much back pressure? How could I find if the unit overheats?