oil preasure up and down like crazyneed help!

I just bought a 93 3000GT SL from a dealer
and i've noticed that the oil presure reading on the guage goes up when i press the gas when the car is movind and also when the car is idling but it also goes back down slowly when i let go of the gas and back up when i hit the gas again.
also ive got white smoke coming out from the back
could this be related ? what coud be the problem
will it be expensive to fix? im sorry to ask so many Q's its just i dont know what to do :banghead:

i think for most cars when u hit the gas the oil psi will go up. likewise witht idle, i think the oil psi goes down, when u are driving normally without accelerating the needle should be fairly in the middle. I dont know what the white smoke is from though, sorry.

white smoke... ah i have this problem too but it does not effect performance from what i've researched of it, god im so tired right now so i can barely remember the cause of the smoke (only that the dealership said it was about 900 to fix) im thinking something with the valves. they are related but not connected with each other, i think the white smoke is the smoke from burning oil (though from what i've heard the color is supposed to be blue?) but white smoke is not uncommon for our cars specially as they get older

Yeah, I think I noticed that there was white smoke coming out of my exhaust pipes too. And it was after I drove so I don't think it's because the car is cold. So based on the diagnostic from Team3S:
http://www.team3s.com/FAQsmoke.htm
it could be bad. :( How would we check to be sure what the problem is? And how much would a head gasket leak or a cracked block or cylinder head cause to be fixed? Damn, I'm so broke already this aint funny....

Sometimes when the head gasket is blown you will get coolant in the oil. This can be seen as bubbles in the oil on the dipstick. A cracked head can cause the same symptoms. Ether way you'll have to remove the head. I would do compression check before removal to see how good the valve's are. Generally you can visually see a bad head gasket, you might have to have the head x-rayed. the worst problem would be a cracked block: look for new motor. Labor is the big cost here. You can do it yourself if you have the right tool's and time. A digital camera would help so you can put it back together.

White smoke out the exhaust is coolant being vaporized. And coolant can only vaporize and be expelled as exhaust when it is being burnt in the cylinders...sounds like a head gasket ;)

If the white smoke smells sweet it is coolant, which is a cracked head gasket. If it smokes only on start up then it could be condensation in the exhaust. If it only smokes on idle and not under load(while driving) and clears up after the car warms up it will be your valve seals.
-Ryan

thanks guys for all of of your help im going to have that checked out today. i'll get back to tell you guys what the problem was once again thanks for all your comments and advice