Does anyone know what the maximum boost level should be set to on a good map
cheers

Ashcossie wrote:Does anyone know what the maximum boost level should be set to on a good map
cheers

Depents on your turbo

Generally I don't tend to go 150-200mb above standard, on stock turbo set up.
I believe the boost on the 150hp will be about 1.5bar

gitko has answered correctly. The maximum pressure depends on the turbine which is established on the engine. Sometimes on the engine put different turbines (turbine type, the manufacturer). Possibilities of increase of pressure at them also the different.

i think the turbo is a GT1749V

It is very difficult to me to answer in English if it was in Russian - all would be very simple. But I will try to answer why it is impossible to raise pressure strongly. Only small parts when I will have a free time.
If you had a turbine with wastegate, on it the maximum pressure created by the turbine is regulated. Then it would be possible to take data on the pressure created by the turbine, from directories on turbines. But at you the turbine with VG actuator. And for this turbine at the test banch this parametre is not regulated. It can be adjusted only in maps.
In the evening I will try to explain why it is impossible to increase pressure and why for different turbines of a consequence can be different.

Each detail has safety factor. It defines how much as much as possible safe loads exceeds real forces in the mechanism on usual modes. Factor of durability do not do big. It is caused by the economic and technical reasons. From positions of economy the detail should be less, it is easier and from rather inexpensive material. Too most and from a technical position.
The most responsible and loaded details in the turbine is a shaft & wheel, compressor wheel, bearing and thrust bearing. That the turbine increased RPM faster wheel and shaft should have the smaller sizes and weight. For this reason safety factor cannot be big.
To increase pressure to you it is necessary to increase turbine RPM. The parity between increase in RPM and pressure has a nonlinear proportion. That is, to increase pressure twice to you it is necessary to increase revolutions much more than twice.
The forces operating on a detail, are proportional to RPM in the second degree.
Thus, if you increase RPM in one and a half time loadings will increase more than twice.
Excuse for bad English.

Continuation tomorrow.

Thus, we see, that at pressure increase in one and a half time, loading on a detail increase almost three times. It on a limit of reliability of details.
But it is fair, if the engine and the turbine are serviceable. If there are any defects loadings can be considerable above that will lead to turbine breakage.
If you have leaks in an air route from the turbine to an input in a block head (branch pipes, interculer, an inlet collector) the ECU will increase as much as possible a signal by the management valve actuator. And that the turbine could create necessary pressure, it will be necessary for it to have considerably big turns, than it is calculated initially. That can lead to its breakage.
If unbalance turbines mismatches norm, but loadings on a shaft and bearings can be several times more settlement. It also will lead to turbine breakage.
If pressure of oil in oil system below norm on LL and on the big loadings, it leads to their intensive deterioration. And it too conducts to turbine breakage.
If the gauge of pressure of boost shows underestimated value pressure it also will cause malfunction.
If the air filter is littered, it also can cause malfunction of the turbine.
I can name still the reasons which can lead to malfunction or turbine breakage, but you I will not continue to frighten. 
You can tell, that before tuning it is necessary to check up all these factors and to eliminate them. You are right. But not from these factors you can check up all. You do not know a technical condition of the turbine. Even if you will check maximum radial and axial play a turbine shaft is yet is not a final indicator of its technical condition. You do not know unbalance the turbine, namely it is the basic criterion of serviceability.
The maximum turns of a shaft from 70000 to 150000 turns in a minute have the majority of turbines. Unbalance a shaft and wheels on these turns should not exceed 1.5 g. It not real, but relative size. If unbalance it will be considerably exceeded, loadings on the turbine will very strongly increase. It will lead to its very fast breakage.
That to you it was clear about what there is a speech, next time I will result typical schedules unbalance which receive at special test banch.