Volvo: 940 Turbo wagon poor acceleration, also dies, oil levels, turbo wagon

Question
I'm a poor college student who is need of some help.  My 940 Turbo wagon is having some problems when I accelerate and sometimes when I come to a stop.  When I accelerate it will sometimes suddenly feel like I'm towing another car behind me then after no more than 45 seconds it will go back to normal.  During this sudden poor acceleration period I notice some white smoke from the back of the car and the car starts to feel rough and shakes a little.  Also it has died a few times as I pull up to a stop.  It doesn't die suddenly as I can feel it coming.  The car will start right back up.  Took it to the shop and he found nothing running the normal tests, coolant and oil levels were good.  Any advice?  Thanks,
Taylor

Answer
Taylor,
If the shop only looked a coolant and oil level, get to a better shop that will drive the car with you so the tech can feel the problem. So many possibilities, intercooler or hoses, Air mass meter, fuel filter, clogged exhaust system, in tank feed pump. Your car will need to spend time at the shop so it can be tested over and over until something is found.