can heart bypass cause high BP?

I havea triple bypass three and a half months ago, am doing very well, back to my routine of hiking hills everyday,(4-6 miles), working, etc etc. When I came home from hospital, I bought a BP machine to montor my blood pressure and typically, it's 110/65ish, resting hrt rate of 65-68 kind of thing; but in the evenings, almost without fail, I'll get an hour or two of increased hrt rate (80-85) and BP sometimes goes as high as 160/70...I'mwondering if this is a mental thing for me...or does my blood pressure fluctuate that wildly throughout the day.....mornings it's good, noon is fine, just in the evenings is where it goes wonky...I'm taking 12mg of metoporlol twice a day, but hoping to wean myself off that stuff over the next three months or so.....