5.7 tuneport,starts fine,up untill opererating temp is reached. When reverse or drive is engaged, motor wants to die,unless you give it a quick throttle response. If it does die it will start right up again. it does not act this way while warming up, over the last year or so i"ve replaced the idle air,throttle pos. sensor, computor,temp sensor,did find a vacume leak behind the throtte body,put a new gasket on.No one can seem to find the problem, also checked neutral switch, changed the 02 sensor