My brand new completely rebuilt 355 has a problem with dieseling when I shut her down. If I have just pushed it pretty hard and hot before I shut it down it diesels. Like tonight I came home and drove up this like 1/4 mile long pretty steep hill at like 60mph in 3rd gear. Probably pulling close to 4000 rpms up it. I get home and shut it off and it diesels. Anytime I push it like that then shut it off it does this. Think maybe its getting so hot it keeps combusting? Not like its carbon buildup I mean its a brand new engine. I run 89 octane doubt thats the problem though.