Cars fitted with an Electronic Control Unit (ECU) have a microchip at the heart which regulates and monitors air flow, fueling and exhaust as well as other integral parts of the engine. Chips can improve fuel efficiency, economy, improve drive-ability and iron out flat spots......perhaps therein lies the answer!
So far as I know, all Trionic turbos, including LPT, rely on the MAP sensor. The fuel cutoff is an integral function of the Trionic ECU (as is just about everything else to do with the engine).
Reading between the lines, if you are thinking of raising the limit so you can up the boost a bit more, then the only way I am aware of is to reprogram the ECU. You could try to interfere with the MAP sensor's perception of the world, but that would cause you even more problems.
Hmm... well there are *certain* things you can do to improve performance by nobbling sensors, but you need to remember it's a risky business.
Fundamentally, you only get any step gain in power output from a turbo engine by winding up the boost. That's easy. What's not so easy is adapting everything else to make sure it happens safely. ECU's have a pre-programmed mapping of adjustments for things like fuel, ignition advance etc. That mapping has a limited design range. It will take a certain amount of boost over standard but then it can't cope. Apart from allowing a higher boost before cut off, re-mapped ECU's from the likes of Abbott, Hirsch, Maptun etc also alter the fuelling and ignition mappings to cope. This not only helps the performance but also protects your engine.
That said, if you really want to try it (not something I recommend) then you can wind the boost up by several means- shorten actuator rod, bleed valve, Dawes device, manual boost control. Trouble is on a standard ECU you'll quickly run into overboost fuel cut off, so the only way round that I've seen is to bleed some pressure from the MAP using another MBC valve. There's a bunch who do this in the States (Swedish Dynamics), pic shown below:
The MAP sensor itself is the black unit with the Saab sticker on top to the left of the blue MBC valve.