1991 Other Mitsubishi Models Changed timing and balance belt

I just changed both the timing and balance shaft belts on my Mighty Max pickup. I followed the manual to the letter EXCEPT for the step where I was supposed to put a screwdriver into a hole in the block to keep the balance shaft from rotating. I was very careful to mark and make sure the balance shaft didn't move during the change. Basically, I couldn't determine where on the left side of the block the "plug" was that I was supposed to remove to insert the screwdriver. There was no description of the plug - whether it was screw-in, or press-in or what. All I really saw were the freeze-plugs.

So it's now back together and running - and all seems well with acceleration and such, but at idle, I swear it vibrates just a bit more than before. Once under load, I think it is the same as before.

Is there any way that I screwed this up? I'd love to know where the plug/port is and would line up the timing marks again and check the shaft with a screwdriver to make sure.

Thanks,
Randy
Keller, TX