Here are some suggestions for getting past the plateau of growth that have worked for me when concentrating on making my chest grow (pectorials have been a very stubborn muscle group regarding my growth):
1.) Work the body part only when you feel the muscle has thoroughly recovered from the previous workout. If you body singals you to work the body part only 3 days after you last worked it, do it as long as the body-part is not still sore. If you are not fully recovered for 8 days; so be it. Wait 8 days before you work that muscle again.
2.) Plan your workouts so that one or two rest days fall immediately after the day you work the muscle you're trying to make grow. Why? Because, we grow when we rest. It gives that muscle some extra time to absorb nutrients, to rest and to grow.
3.) On your rest days mentioned in #2 above (the ones that follow the day you work the difficult muscle), REST...don't play racquetball or jog or do any thing that would add to your maintenance calories. Just rest and EAT.
4.) Use the rest days mentioned in #2 and #3 above to eat like a mad man, on schedule.
Doing this has helped me to build-up stubborn muscle groups.
Comments?