It's up to you i think factory is 7psi.
Suggestion is to get it to a diesel tuner . 12-14psi up you need a intercooler etc (front is better). More than 14 you will need to look at changing fuel pump etc.
The one in this link runs 21PSI with a lot of help and some serious mods to fuel pump(14B-T), timing gear (14B-T)
http://https://forum.ih8mud.com/70-series-tech/724139-13b-t-rebuild-needed.html
and everything needs to be working well if you turn up the boost. Coolant (not water) , oil, oil pump etc,
then there is this one which is close to home for you to relate to
https://forum.ih8mud.com/70-series-...t-bj74-tough-offroad-all-rounder-buildup.html
And you need gauges EGT (will stop you busting the engine and will show you puting the boot in at low revs does not work) , Oil Temp (shows you if oil getting low and hot), Water Temp (shows the toyoyta one is CRAP), Boost (tells you when loosing boost or going over or close to max).
When my 13B-T engine is finally running again I will docuemnt it more but here is a run down
1. 14B-T timing gear
2. 14B-T Fuel pump modified for 21psi of boost (single setting)
3. 7M-GTE turbo modified - boost start 1700rpm 20+psi by 2200rpm change up 2500rpm
4. Intercooler - mine is front mount
5. Modified intake to allow more air through.
6. Bad attitude driver
7. Now new Gauges as per above
8. A mechanic who likes and knows diesels
9. THis is not a highway queen every panel is dented from jungle adventures
10. Forgot the exhaust 3"
