1997 S70 'Red' Turbo Vacuum Line

[coop]

From what I’ve seen it could be either from an air leak but if you’ve replaced the vac lines and checked everything off the radiator and intercooler then tbe issue could be a dirty/bad maf. Easiest is to just unplug it and start the car and see how it runs vs with it plugged in.

You may want to eventually replace the air box with a stock one. Cone/k&n filters can cause issues especially with the maf.

[Vuym]

The red line is a pressure line which takes pressure from the turbo to apply pressure to the watergate with the yellow hose. Pressure on the waste gate holds it closed and allows boost to build. The blue hose dumps any unused boost pressure back into the snorkel just upstream of the turbo

The TCV valve decides how much boost to send to either the waste gate or dump it back into the blue hose.

None of the hoses see vacuum. They need clamps to stop from popping off

Thanks abscate, that's really helpful I didn't quite understand how the TCV regulated the wastegate. I've popped on screw-type hose clamps on each end of each TCV hose too.