Intermittent Hard Shifting. HELP!!!

[millencolin360]

my car (automatic) shifts very hard at intermittent times. the trouble code that comes up is " P0122 - Throttle Position Sensor Switch “A” Circuit Low Input." ive had the tps replaced 2 times and the problem went away for about a month. now it is back. if the car starts shifting hard and i turn the key off and then back on it will drive normal for awhile and then start doing it again. sometimes i can go 2-4 days without it acting up. its totally random. it also idles funny when its acting up. the subaru dealership had it for a month and all they could do was replace the tps that they replaced the first time. can anyone help?!?

thanks