cams are camshafts that open and close the valves. twin cams means 2 camshafts.
twin turbo'd are 2 turbos. any toyota engine(to my knowledge) with a "g" is a twin cam engine.
ie- 5mge<---6cyl, twin camshaft, electronic fuel injection
4afe<-----4cyl, economy head, electronic fuel injection
3sgte<----4cyl, twin cam, turbo, electronic fuel injection

Here is a link that explains what PSI is, but is complicated.

http://www.answers.com/topic/pound-force-p...per-square-inch

Basically it is a measurement of pressure applied to a 1" square suface, by whatever substance, generally air (a gas), or liquid.
Thus, there is pressure (psi) in these systems: turbo boost, engine oil, fuel, automatic trans oil, radiator, power steering, brake, tires, and (on some cars, air shocks).

And remember this, pressure in a system can be dangerous if there is a problem, or opening it up, and most systems under pressure are hot.

thank u very much. i havent read the link yet but i'm sure its going to help alot. if u know anything else there is to know about a supra could u guys feed me the information?