hi, my s70 starts and drives ok then after anything between 5 to 10 km (3 to 6miles) surges or slows down or cuts out, often i cant get the revs up. then sometimes it starts immediately and at times i have to let it rest, then ditto again...., not spark plugs, fuel filter, air filter, clean throttle body, etc, any ideas please?

 

A few thoughts - could be the coolant temp sensor (easy fix - $15 US part on FCP Euro) or could be a fuel pump relay (sometimes the relays get sticky when they heat up and by resting it cools down and goes normal). Also easy fix - $30 part or so. After checking those two I'd consider cleaning the MAF or testing it out.