Vortex speed gain ?

[fender]

Not that I'm complaining, but I gained 5fps after unstringing in Dec/12 and restringing last Saturday.
A little info: New Vortex in 2/12.
After serving issues on two Ecal dacron strings I decided to try a Wyvern custom string( not sure what material it is made from). Wyvern string has lasted well and put through a Pro Chronagraph was consistant@ 314-316fps last year. This year I noticed I was 2-3 inches high at 30 yrds when I sighted it in, so I made adjustments to zero. After thinking about it I got out the chrony and was seeing 320-321 fps,which explains why I was hitting high. I did reverse the string when I restrung, but other than that, nothing that I can think of has changed in cluding brace height, outside temp and shooting 10 feet before the chronagraph.
Any Thoughts ?
Thanks