I've read some of the threads on making the LED trouble code reader, but I'm still a little lost. I haven't seen any posts directly regarding reading codes on a 1992 190E 2.6. My car doesn't even have a check engine light, but I do have 2 "ports". I have a round one over the driver side front wheel well and I have a square one in the battery compartment. Which do I use? I've seen two diagrams for the diy code reader. Which is the latest one? Is there a guide to using this code reader for my particular car? The only real issue I have is lack of power (compression test shows good compression). I got this car recently and I just want to make sure everything is working as it should. Thanks so much for your help!