First off, Awesome site. I've learned a lot about my truck in the past few days. I would like some help as I get to understand these trucks. 1) How do I tell if my engine falls into the 'RENIX' category? I have a vacuum leak that I will be correcting. After reading some post on here, it was suggested to replace all of the lines as they are 30yrs. old. The part #'s were given ( Napa part number BK 715-1367,Napa part number BK-715-1366.,part number 715-1365.) by cruiser54 but I noticed it stated it was for the 'RENIX' model. I'm currently only blowing air through the defrost vents as no other vents will blow. I also have an irregular idle that sounds like your flooring it on start up. It will die down after 1-3 seconds, then idle between high and low whenever in park or neutral. Regardless of the temperature of the motor. If the truck is in gear it idles perfectly. Thoughts? I appreciate any help in advance. Looking forward to getting this little gem running like a top.