My first time on this site.it is great. Question, when installing my trunk pulldown motor ,97 sts,it sounds like the bolts are cracking the plastic.the hole sizes are the same but i didnt want to break it. Is this normal

 

The screws make grooves in the plastic during the original install. When you replace the screws you have to turn them CCW till the screw threads line up with the old screw grooves then turn CW to fasten.
Good luck.