p0740 code

i've replaced master cylinder,front pads (ceramic) changed tran fluid & filter, also replaced tcc pwm solenoid, and the lockup solenoid. the reason i changed solenoids was because of hard shifting (the tcc/pwm solved this)changed the lockup solenoid also, cleaned egr valve, ran a can of sea foam thru gas tank, also ran a can of gm injector cleaner thru gas tank. changed alternator, has about 85k on it. has always run great and started right up.. gas mileage was never very good , 13-14, after seafoam/gm cleaner now 16-17, runs good, shifts real good, but ses light is on and reading p0740.
wife complained when pulliing up to park sometimes it would die.
now problem is when coming to a complete stop, it comes to a stop but sounds and feels like it wants to move forward i can hear the rear tire trying to grip in stone drive.
but last week the prob was when at a complete stop(without previous problem of stoping) and taking off if would hesitate, this week hesitation is gone, i pulled electrical connectors off trany and checked for voltage, which was there and now the prob is when coming to a complete stop, it seems to go away after warm up, any idea's .... i was thiking ignition switch, but would like to know for sure ??? thanks, also.the only code im pulling is p0740, after i erase start eng ses appeas within 30 sec's oops 99 blazer 4.3 4x4 automatic.