The stock headgasket can hold a fair amount of boost in a properly managed engine. In an improperly managed engine, it cannot hold as much. You can put a better head gasket in an improperly managed engine and it will hold and you can break other components instead, like pistons or rods, for example. You can buy better internal parts and put those in an improperly managed engine and they will hold longer before something lets go.

Your best bet is not to exceed the limitations of your stock engine management or, if you do, overcome those limitations. Your motor is the weakest B230FT made. Several improvements were made over the years, but your motor has none of them. I would not push it as far as you seem inclined to.

Determine the limits of your fuel system and do not exceed them. Determine the limits of your ignition and do not exceed them. I could give you this information, but it would be better for you to learn it yourself since it appears you are determined to play with high boost, but have only a limited knowledge of what is required. The kids at Turbobricks can fill you in on the details, but be careful whose advice you follow there as many of them write about stuff they have no experience with. Find the ones who have actually done what they write about on an engine similar to yours in terms of the version of B230FT and level of mods, and who have tested what they advise for at least a year with good results (many of the kids have only been driving for a couple of years), and listen to those people. They are the ones who can help you.

My advice is to make sure your engine is in perfect condition. Do a service, tune up, and compression leak down test. Send your 15 year old injectors out for a cleaning. If all is perfect, on an otherwise stock motor running premium gas, 11 psi is safe and you can experiment with 12-14 psi if you know what you are doing. More is not advisable. Do not be surprised if your 15 year old headgasket lets go. It probably will soon anyway. Its a great opportunity to rebuild the head, which probably needs it.

Philip Bradley
Good luck.