its a vane type mounted before the turbo intake. It has a fault code operation but evrything is working. I tried even changing the computer but it made no difference.

is the air flow meter a vane type or a hot wire, or thick film type?
also where is it mounted? as in before the turbo intake or between the turbo and the manifold? it needs to be before the turbo intake for most consistant operation.
is it possable to get trouble codes out of the ecm? the ones here (colonies) have the ability to at least give a flash/check engine light code.

the system is originally off a normally aspirated 4 cylinder engine and uses an air flow meter. It is multi point injection not single. Fuel pressure is 200kpa at idle and 250 at zero vacuum. This is fine according to the service manual.

OK, most GM efi systems use a Bosch design as do most manufacturers. a vacuum controlled pressure regulator in these systems uses manifold vacuum to LOWER the fuel pressure at ide and at cruising speed
the lack of vacuum will cause the fuel pressure to increse to whatever the maximum designed pressure for that system is. later systems incorporated an ecm controlled vacuum solonoid in line to block the vacuum at startup under hot conditions to help eliminate "hot soak" hard starting. this too causes an increase in fuel pressure and thereby allows MORE fuel to be injected durring the injector pulse.
there different ways to increase the amount of fuel injected, the most obvious is to install larger flow injectors. but one can also increase the amount of fuel pressure and gain added fuel. another way is to make the ecm think that the engine is cold and this will cause it to go into cold start enrichment, doing this will lengthen the injector pulse which along with higher fuel pressure will accomplish the same as putting in larger injectors.
all of this does not, however explain the original question as to why he is experiancing fuel shut down under boost.
assuming that the system used was intended for a normally asperated (nonturbo) application, AND assuming that the system has a MAP sensor, the answer is simple, the MAP sensor senses the boost and the ecm interpets it as a backfire and shuts down the injectors. something that is designed into the system to prevent engine fires.
a POSSABLE remedy is to get a MAP sensor for a Saab 900 turbo and try running it to see if it will allow the ecm to interpet things correctly. the systems used on Saab are also a delco system and should be compatable.
good luck

My bad...I assumed most turbo engines had rising rate regs as my last efi turbo engine had a fuel pressure regulator that was hooked up to a boost/vacuum line as was the MAP sensor.

I agreee with the comment about the MAP sensor on the delco not being able to read positive pressure is most likely your problem.

Craig

Chris, I agree with you with the regulators, spot on.

Some injectors will not allow the additional fuel, which is not much at all anyhow. Only reason I would use a rising rate reg is with a modified fuel system for tuning.

Another point of interest, rising rate fuel regs do not increase at a set rate according to boost level. A little hard to explain, however there is not set relation between the 2, i.e 1 pound of boost gives you another 2 psi of fuel pressure. This DOES NOT happen.

I think i made sense

You need a 2 or 3 bar map sensor, the Camira map sensor will not measure positive pressures.

Most MAP sensors don't sense boost; they have to be designed for the particular range of plus and minus pressures. The kind that sense boost are more expensive. So the question is valid -- did your system come from a turbo car?

Rising-rate regulators are just one way of fuel management. It depends on how the system is designed. In 99 Ford switched from rising-rate to non-rising rate, and that's on the non-turbo 4.6 liter. Interesting question about "undersized" injectors. The factories use rising rate, but aren't driving the injectors at pressures higher than the spec'd pressure.

I thought that rising rate regulators were only for people who wanted to use undersized injectors, so that they retain good idle, and increase the pressure on boost to get adequate fuel volume??

Regular EFI/Turbo cars have a high pressure regulator, but they aren't rising rate. Although if my memory serves me correctly there are 2 pressure settings on the stock CA18 fuel pressure regulator. Primarily to improve starting performance of a hot engine.

The CA18 Fuel pressure regulator is controlled by a solenoid which is controlled by manifold pressure and the ECU. The ECU takes information from the ignition switch, air flow meter, temperature sensor, and crank angle sensor to figure out what pressure is required.

This is described in the S13 Silvia Factory Manual, on page EF&EC-20.

If anyone can enlighten me more, then great.

You need a rising rate fuel pressure regulator at least. All factory turbo engines come with them. Also a map sensor does sense boost as the map sensor takes it's reading from a line that experiences boost and vacuum. Check that the line that is running to the map is experiencing boost and vacuum.

Craig