The different number means the ratio.
Modded are just stock rockers that are re-welded to have a higher ratio
Rollers are lightweight rockers that are way easier on valvetrain parts...but you pay out the ying yang for them.
This is a response from Will I got last year in contemplating the rocker and Tb install.Glad to hear you got all the bugs worked out man. Get it re-tuned for those 1.9's though as your final mod![]()