I have a 2000 chevy silverado z71 vortec engine v6 that idles rough and has a constant CEL flashing. Late october of last year I let my sister borrow my truck to help her and her husband get to and from work and pick up there kids because they had to do that all with one car so i figured it would help them out a lot if they had a second vehicle. Couple weeks pass and she calls me and tells me she starts the truck and noticed it started to idle bad like it wanted to die and also had the CEL flashing while both driving or in a parked position as well as at red lights. I know its not good to drive around in a vehicle in that state but she continued to do so for a day or so until i got my truck back from her. Immediately i cautiously drove it over to jiffylube where one mechanic kindly hooked up his inexpensive (minor if you will but still helpful and better than nothing) scantool for free and i got the codes p0430 and p0300. 6 days later i replaced the sparks plugs and wires but still had the rough idle and blinking/flashing CEL. And before doing anything else i drove the truck over to oreileys this time rough idle, flashing CEL and all to check codes and they had somewhat of an upgrade i guess you can say to that of jiffylubes scan tool (bigger more buttons but still no tech 2) and i got 2 new codes p0135 p0141 along with the already prior diagnosed p0300 and p0430 codes. Keep in mind this is after the plugs and wires smh. Since then the truck has been sitting for 5 months and im just now getting back into the works now that the warm weather is slowly melting the snow and giving me back my natural outside 4stands and a carjack worshop. I did pull the battery out to prevent any damage to it from the extreme cold winter. So ive replaced the spark plugs and wires and am now considering moving on to the fuel filter, O2 sensors, fuel injectors, vacuum test for leaks, and then a crankshaft relearn at my local chevy dealer. If any of these dont fix the problem then its on to the cat converters and instake manifold gaskets. Thats my full story though and i hope somebody can help me out please and thanks in advance!