I have a 2000 fourwinns with a volvo 4,3gl perfs sx drive(black).Have a wot issue .when going to 3/4 to full throttle motor just bogs, back off throttle and goes great from 1/2 to 3/4throttle .everything from timing to ignition to carb(new holley 2300) have been gone thru and or replaced.Can a ignition module from a auto version be the possibility.not sure how the engine advances timing.was reading forum and there could be a maybe its the exhaust flappers,but im not sure if this engine even came with them,if so where r they located.thanks greatly appriciated