Hey Tony & welcome to the forum
glad you got your problem sorted.. happy boosting
what gauge have you got? are you talking bout the factory boost gauge?
i would think the first & best mod would be a boost gauge with vacuum... it will tell you straight away if you ever have any problems related to air
usually the reason exhaust manifolds leak is because of the manifold bolts, sometimes you may find that the threads in the head are stripped and the bolts refuse to tighten and just strip it out worse
but if yours tightened up sweet... then minta
have a supra day