Hi David, The set screw uses a hex allen wrench, 4mm I think. Plug the hole after making adjustments. I've seen everything from a golf T to a wood screw to plug the adjustment hole. One of the DeLorean clubs sells a nice little plug with a handle on it for easy removal, unfortunately I don't remember which one, check the archive's. There are directions for setting the CO on my web page at: http://personal.picusnet.com/dsontos/tuneup.htm Dave Sontos VIN 02573 Delorean17@xxxx wrote: > Hello, > I have been working on my project car for some time now and havent been > able to figure out its odd idle and poor acceleration problems. The frequency > valve is working properly so I thought the problem may be related to the > intake system. > I thought it might be a good idea to check the co levels and adjust the > screw as necessary. I removed the intake(both halves) and found that the > metal ball(plug) that covers the hole was missing(nice sized vacuum leak I > guess). It also looks like the screw is in as far as it can go. I am > guessing this could be my problem although I dont know for sure. Where can I > buy one of these plugs at? also, what type of head is on the co mix screw? > you cant really see it through that little hole.