I recently looked under the hood thinking about what to do as in engine detailing and painting. For the up and coming Pontiac day next year at Englishtown,NJ.
I glanced over at the fuel pressure regulator(because it is shinney) and bam.
I had a perforrated vacuum line to the pressure regulator. Didn't hear a peep from the engine in regards to a vacuum leak, car ran and started fine, the idle was a slight bit lumpy but just alittle with 116k plus thought it was normal.
I look around my tool box and found some vacuum hoses, I had to slip the skinny one into the fatter one because the ends of fittings are different sizes.
Buttoned it up and took her for a spin, noticed a big difference right away in response even squealled the left front tire a bit.
So when checking your vacuum just don't look at them, apply pressure to them bend them check for cracks and perforrations.
My tip for the day.

Spank you very much. Great advice. I've been bitten by small leaks twice on my car.

Good tip

-and I find it interesting to think about what potential effects (if any) that would likely occur with that vacuum line completely off. AND your expressing that everything was still running just fine is exactly what I'd expect. Here is why: with that particular line disconnected, the regulator increases the fuel rail pressure by 10 psi (from about 40psi to 50psi) -which should not cause any changes in engine operation. Also, the small amount of vacuum leak caused by that small line will also not affect normal engine operation. (-even at idle.) BUT I'm sure that GM had good reason to not run the pressure at 50 psi all the time. :?:

So, in my mind, that lends even more importance to your good advice of checking things over thoroughly.

PS. -speaking from personal experience this last weekend with other fuel system problems, which involved checking the regulator for proper operation by reading rail pressure while alternately removing and installing that vacuum line.

Wow ... deja vu.

I had my car looked at today, and we noticed one of my vacuum lines cracked away.

Great tip...

I found both of mine on the throttle body completely cracked. Had to go to the dealer to get the replacements. Car ran shaky too...all good now.

Thanks for the tip. I'll be sure to check my lines.
What does vaccum do for the regulator anyway? Increase / decrease?

pressure regulator increases the pressure by 10psi when vacuum is absent.

After owning several turbocharged cars, I made it part of my weekend routine to check all the vac lines, as they would also carry positive pressure under boost...which means lost boost if they went bad :( .

Speaking of turbo cars, I found a turbo Grand Prix just languishing here in the area. How common or rare are those?