That's really clever!

I thought about it, and i worked out to do it really neatly, you'd need two tee pieces and a pair of check valves. That way the most that the MAP sensor would see is about 50kpa of boost (half a bar, 7psi) - but it'd still see a full vacuum signal when there's no boost present, and it'd still be able to sense atmospheric pressure.

The solution I came up with is

- Run a tee from the diaphragm line on the other side of the restrictor
- Check valve so that positive pressure only comes out
- Tee it in before the line to the 3-port solenoid input
- Add a check valve so that only vacuum comes from the manifold

Incredibly difficult to describe, so i present for you this very bad diagram:



Would that work - am i right? As far as i can tell, that ought to let you run a lot more than factory boost, and if you added a variable restrictor, you'd get it up to 1.5 bar easily.