Removing a minimal amount of material can remove hot spots and have a great effect on performance. The combustion chamber doesn't provide any tumble effect other than it's general shape and position. The casting bumps should be removed.

http://www.bnmotorsports.com "And I will strike down upon thee with great vengeance and furious anger those who attempt to poison and destroy my CEG brothers. And you will know I am the Moderator when I lay my vengeance upon you."