I can't figure out which sensor to buy. It seems every web site has a differant part number for my truck. I want the front upstream air/ fuel sensor. I have a 2001 Tacoma base 4x4 with the 2.7. The truck was assembled 09/2000, which has been a nightmare buying parts for the 11 years that I have owned it. I would go to my local dealer but they kept ordering the wrong parts last time I went there, they even used my vin number. I am pretty sure I should just buy the most expensive one that has always happened.