The ARC valve does thee things -- causes your cruise control to surge like crazy as it switches in and out, dumps the boost when you don't need it but leaves the turbo spinning (to help eliminate turbo lag) and supposedly lets the trap oxidizer warm up more slowly to prevent it cracking.

You can live without the cruise control surge, I'm sure. I can, anyway!.

The boost cut while flying down the highway at low throttle will probably save you some gas -- I got 36 mpg on the last tank before mine quit, only 31 after. Not a big deal unless you do a lot of highway travel in light traffic.

The turbo lag elimination may or may not be a benefit, I didn't see much change.

I suspect it is there for the trap oxidizer more than anything, and you don't have one anymore.

I don't think anything will be different with the ARV blocked, certainly no extra wear on the turbo. However, if you can hear the air whistling when it opens up, I suspect your air filter to turbo hose is shot, you shouldn't hear either the vent or the turbo!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!