I've got a 94 z28 with the obdi and the 12 pin connector. I purchased a tune recently from madz28 and i'm anxious to upload it however i can't connect to my pcm!!!! The cable i bought was from mastach.com i've got it hooked up to the ground pin a and the data port pin m? The cable tests fine, but all the software ever does is wait, time out and say that there is no response from the pcm? BTW if the ignition is off i get the error messages instantly, but with it on it takes about 30sec to a min before i get any error messages. Any ideas?