I recently pulled out the motor to swap in an M46, but since I've reinstalled the motor I'm getting pinging while under load. I believe it is a single cylinder because it sounds more like a ticking then a "can of marbles" that you normally hear when all cylinders are pinging. I know the pistons are all perfect with no detonation damage, as I had the head off a couple months ago, and the head is in good condition, no chamber damage or anything like that. Any idea what would be causing this? I did notice when I had the intake mani off that the #1 intake port seemed browned, like perhaps the injector was spraying a little to the side rather than straight on... would this cause pinging? I just put 91 in the car to see if the issue was octane, but it persists.

Thanks,
Phil