Driving down to the parents on Friday and I get up to 80mph and put the cruise on. It slows down to 78 then accelerates up to 81 the it feels like it just lets off the gas and speed falls to 78 then fells like the accelerator kicks in and up to 81 again. It feels really weird so I look at my boost gauge and its bouncing around. when its accelerating it goes up 6-7 psi for normal accel and then falls down to 10hg before it starts to accel again up to 6-7psi. It does this the whole way down and back and its kinda of annoying.

Any idea's? Vacuum problem?

 

There's a lot it could be, but one thing not to ignore is that the B5 is known for cruise control problems. It may be that your cruise control is gonna go ****-up on you, and the fluctuating road speed is being caused by that. The boost would change accordingly as the F-ed up cruise control moves your speed setting around and the car coasts and accelerates. Just a thought...