Speedo Help!

I had 245/50/16 tires and went to 285/40/17. I used to run at 70mph at 2000rpm, now at 2000rpm I'm doing 67mph. Am I running faster/slower or is my rpm's off? How can I fix it,only w/ a reprogramer?

I used a Hypertech Power Programmer III. It allows you to adjust for different tire sizes and gear ratios. I think the Predator might do the same thing if Im not mistaken.