Cam choice

To choose a bigger cam, you first need to know WHICH Purple cam you have. The Word Purple by itself is somewhat meaningless.
If that cannot be ascertained, then you really need to know your exact Compression Ratio, to narrow your cam choices down to two or three. But
remember; each bigger cam will push the operating rpm up about 200 rpm, taking about half of that off the bottom. So it only takes a couple of cam sizes to ruin the bottom end of a nice street combo, which you will have to spend more money on, to recover.
So, if you really like your current combo, then it would seem prudent to replace the flatted cam with another same-spec cam. Jus my opinion.