M
2009 assault, motor ran good it was having a little stumble around 5 to 6000 rpm and would only hit 7900 wot. i read a post that some of the exhaust valve gaskets had too big of a center hole and were blowing out, so i checked my and they were blown out.i cleaned them and the small hole going into cylinder was plugged. cleaned everything and put gasket from a 2015 in it. now it will bog right out at half throttle and if you hold it there it will surge up and down. runs fine full throttle and idles good. does hit 8200 now.is there a reason this gasket wont work?