I had the same problem for the last 2 years untill 2 day ago when I was able fix it myself after spending one month and a half all together in shops,dealers and over $ 900 .They all are tech but without the computers ...the are just a bunch of idiots.Last tech told me that it will cost me $8000 to have the trans replaced.Anyway the problem was w/ the idle speed....when the engine was cold ...no problem the rpm is a litle bit higher but w/ engine warm ...at every stop I was feeling the " rear ended" because the throtle control (inside), before intake mainfold had a lot of gease and dust deposits and the engine couldnt breath at low rpm.The dust got there because they were really careless and slopy when they replace the air filter .Need more info I can help