your engine will be breathing more with the rockers so there might be a small increase but hardly noticeable.

when you are up there in miles you should change the springs out for at the very least piece of mind. weather you upgrade them or not is up to you. im putting 1.8's in my base 06 but im not changing out the springs only because they only have 60k on them. if there was more miles on the motor then i would upgrade to the crow cam 105s.