Try this to shock the pecs. I did this today and my pecs were more swoll than they have been in a long time.

Decline DB - warm up and then 2 working sets
1 set on flat setting
1 set on #1 setting
1 set on #2 setting
1 set on #3 setting
and 1 set on #4 setting.

If you need more than 6 sets for pecs, add more, but I can promise you this will fatigue the hell out of your pecs. It was one of the best pec workouts I've had in a long time and it was over quickly because I didn't have to move from bench to bench changing weights and stuff. From now on I will do this atleast once a month.