03 tundra limited,cruise control and strange feeling brake peddle, 173,000 miles.

Here's a new one. While driving down the interstate the other day. running 70 mph with cruise control on no problems at all. I went to depress the brake peddle and it felt a little hard and not the normal feel. After the second press of the peddled it felt normal again. I also noticed a slight noise when depressed. I pulled over to the shoulder put the truck into park and depressed the brake peddle again and same little noise, I thought it might had been from the front brakes but everything seems fine. It was not something that had happened before. Only when on cruise for a while, not say after 5-10 mins. Thoughts? I thinking maybe a small vacuum leak I really do not know.