I'm with tech inspector... the only time i ever had dieseling was thru heat...its a common misconception that it can be many other things... but it is worth checkin the temp...you say its a lil hot...how much is a lil?...colder plugs, new 'summer' thermostat,decent pump gas,maybe even some heatwrap on yer exhaust down pipes n manifolds etc are all inexpensive ways of tryin to fix this..the throttle stop thing is a poss but... the most common cause for it IS heat..i worked on all kinds o engines from 4 bangers to RB211 jet engines and the same can be said.... heat is the devil..
my 55 was a real pain in the ass, it used to diesel when i used it..i ignored it like a dork fer hella days...then i sat in traffic one day and the thing got sooo frickin hot under the hood that the petrol vaporized in the fuel lines...so i jus sat that like a dumb ass tryin to cool em down... try the easy fixes first....use good gas etc.... check ya ignition also etc... jus my opinion but, its a case of the usual suspects.. yknow