I have a 2000 z24 2.4. When I accelerate I experience sputtering until 3000 rpm and then it runs great. I have replaced the plugs and coil to boots. I also noticed that sitting in the driveway while hitting the accelerator hard and winding it up, off and on again, I get a slightly noticeable black smoke out the tailpipe. There has been no check engine light coming on at all, never. I would like to check the coils with my multimeter but cannot find info on how to do so. Also, I want to check things like the MAP and TPS with my meter but again I can't find information regarding specs. Any info or advice would be greatly appreciated. Oh, I noticed carbon buildup on the throttle body, what is a good way to clean the system.