Went from the stock 58mm to a 3.8 72mm and the idle has become horrible. Doing a quick log I saw it now instead of 5-10 degrees timing it has -17 and sounds like the cams are in terrible overlap as it is sucking at the tail pipes. So is it possibly trying to over come some max torque load at idle and doing anything it can to reduce load? I thought I saw a table for timing control used to limit idle or change idle speed at some point but now can't find it or maybe was some other computer as been working on a few vehicles. I did find a table for minimum allowed spark load so was thinking of putting 5-10 degrees in the tables around idle and see if helps but still have the cams jacked up and not sure what would cause them to respond as they did. Just looking for ideas or someone with a cobalt that might have had the issue as read at one point it was popular to go larger on them too.