Hi All I've been lurking for a while now and would like to jump in with a question. My 2001 GMC Sierra SLT -1500 4X4 has an air filter for the ac/ heater vents air. seeing that I have 40K miles on it I would like to replace it but for the life of me I can't find it. Will some tech or other Ng member be able to enlighten me. Also if anyone has a shop manual for an 01 I'll buy it off you if you no longer have that vehicle. Thanks Deane