Originally Posted by Dan-12TTRS
Right, that's normal, unless something is wrong there should be no positive boost when not on throttle.
OK, maybe I should have said "top speed". Even at 70mph you are only using about 10% of engine peak power. Once the power required to maintain speed exceeds that which the engine can produce with no boost, you will have boost at a steady speed as long as the power required is high. Certainly you can see that at top speed, even tho "steady" you will be at maximum boost for that engine rpm (otherwise, your speed would increase!!) At normal highway speeds you will not see this effect!