bigblaze

I have a 97 legacy 2.2 AWD 5speed wagon. it runs awesome untill you drive it for like 5 mins then it wont hardly idle and it only runs on 2 cylinders. but if you shut it off for 30 seconds and start it back up it runs fine again untill it gets drivin. what sensor could be doing this. i heard something about a tranny speed sensor. but i dont know im used to old Subarus. any help would be greatly appreiated.