@ImNoob2009   Thanks for the tips.  I used up all the plant foods early to raise the ZDL so when it gets to the final 10 seconds, I need to be able to kill the plant food carrying zombie quickly to Imp the last few zombies for a score jump before time ends.  I think I can try to do this without a mower launching with my high mastery profile.  
@FantastiXxPVZ. 0.1% chance to boost is still an advantage (when it boosts) so it is certainly not fair for players without. Besides, it has now made my level 10 profile looks odd.  First it was my level 5 profile got converted to level 7 and then advanced to level 8, now my level 10 will be soon changed to be a second M1, I wish EA/PopCap would provide an option to allow player to lower their plant levels since they have removed the ability of creating new profiles.  
As for me, I think I will need to find time to work on a spare low level profile to level 5 soon to enjoy the challenge of mid-level plants again.