My 1998 v70glt acts like it is having a fuel issue. It suddenly loses power, runs horribly and puts off a nasty odor from the erxhaust.
I have re[placed the fuel filter, replaced the pump relay with a known good one and am positive that it has good gas in it.
It may go 200 or 20 miles before it does it again. It seemingly stops when I disconnect the negative battery cable for a few min. and restart it.
Runs great until the next time with no odor at all. Kinda dangerous on the highway.

 

could be the fuel pump on its way out. You'd need to measure the current draw of the pump and the fuel pressure at the rail and compare to spec. My theory is as pumps wear out they draw too much current which can overheat the pump and the relay. turning off the car for a few allows the parts to cool off. I take it you don't have any check engine codes to indicate the MAF or O2 sensor have issues?