2001 mazda 626 2.0

my car will cut in and out while i drive not all the time i have no check eng light on i have replaced the coil pac and wires i have looked at all my vacum lines and do no see a loose hose sometimes i have noticed it will idle at 1000 rpms after a long drive. it cut in and out ussaly around 40 to 55 mph. ive had a tranny guy and a mechanic look at it no one noe what it is. fuel pressure test was good and some days it doesnt do it but now its hot out side it seems to do it every drive if it cuts out meaning it will drop a rpm if i give it gas it will stop doing it