Data Plane Whacked Out (v1.5-alpha)

I’m having trouble with my Istio install, I had installed the 1.15-alpha at some point. I subsequently upgraded to 1.15.2, and now have downgraded to 1.4.7. I have a serious desire to start from scratch. Here’s what istioctl is telling me about my setup:

➜ istioctl version                                                                                                                                         
client version: 1.5.2
control plane version: 1.4.7
data plane version: 1.5-alpha.9be91c3ee53754b665aca1acc3a72b83b08d0c88 (3 proxies), 1.4.7 (2 proxies)

How can I clean this up? Thanks!