long time reader, first time poster hopefully I'll get some ideas before going back to it.
I've got a 91 Bighorn w/ 4jb1-tc and the usual things.
It's got a VF10 with a welded waste-gate, 2.5" turbo back exhaust(no mufflers), injectors flowed/cleaned and I replaced the head gasket after it began to over pressurize, it actually made 88kW at the wheels, blistering I know.
I also changed heads, had it skimmed and crack tested/cleaned valves all checked and adjusted etc, usual stuff you do when doing head work.
However it's begun to over-pressurize again. I wasn't running as much boost the first time as I welded the gate shut after I did the HG, so I'm unsure if 28-30psi of boost is actually the issue.
Before I just buy another head gasket and slap it on, perhaps I need to look at something else? could the liners move/fail perhaps and it's causing it to fail relatively early? It worked extremely well for about 2 months before starting to over pressurize again, and it slowly gets worse just like the first time the gasket went though.
perhaps i just need a 12mm pump and jerry rig a big turbo.