-before any other mods, add a proper intercooler
-do not boost over 14psi on stock turbo
-do not try to increase boost by disconnecting the wastegate pressure line
-stock tds intercooler is okay for max ~15psi
-oil pressure light comes on when boost goes over ~15psi (switch in the overpressure valve below intake manifold, item #9 on the latter picture Tankas posted)
Remember, power doesn't come from boost only. Boost makes engine breathe more, so you can add more fuel, which makes power. Injection timing and length are ones of the major variables. When talking about boost, 15psi isn't the same amount of air in every system (engine, manifolds, turbo etc..). Stock turbocharger running 20psi is far less than for example HX35 running 15psi. Think about this: you have two coke bottles. One has 2mm hole in the bottom, the other one has no bottom end at all. When you put 15psi of pressure in both, which one has the greater
air flow through it?
After all, an engine is nothing but an air pump.
With stock injection pump and settings, you can boost over 30psi and still get less than stock 115hp. If your turbo is big enough to handle those pressure ratios, you'll propably get the stock hp. Trying the same on stock tiny turbo, you'll get (say) over 30psi of exhaust manifold pressure, so actually less air is flowing through the engine than in stock form. In stock, exhaust manifold pressure is much, much less than the intake manifold (=boost) pressure.
Not only high exhaust manifold pressure makes you lose power, but it also means high exhaust gas temperatures and high engine loads. Before you even notice, you'll have a warped/cracked head. Finding an intact used head is almost impossible. Many of you guys sure have warped heads which you don't even know about. Trust me, I know -- I have three cracked heads in the garage.
On a proper turbo and injection settings you can get around 170hp running 15psi boost. That is about the maximum you can get with a decent pump tuning, if you need more, you'll need to upgrade the distributor head and more.
for now...
