Is my turbo working?

I have a '98 Sub with the 6.5 turbo diesel. I'm not sure that the turbo is working because you can't hear any whine and it feels a bit gutless compared to my buddy's '92 1-ton Silverado. He does have the 5 speed tranny in his truck so maybe that's the difference, I dunno.
My friend who is a truck driver is the previous owner and a couple years ago he pulled off the catalytic converter and muffler and ran a straight pipe. It's noisy, but not as much as you might think. As a result, it may be too loud to hear the turbo.
My question is how can I tell if the turbo is working properly? I don't have access to a boost gauge, but is there an economical option available that's fairly simple to install?

I would think if the turbo wasn't working, you would have a bit of smoke.

Normally I take it pretty easy when driving but it does blow quite a bit of black smoke if you romp down on the accelerator. Is the turbo likely to be bad, then?

The turbo will lag behind a quick push of the accelerator, so some smoke can be expected.A lot of smoke,coupled with poor pick up would point to a bad/weak turbo.

1995 turbo diesel. When the turbo was running perfectly it made no sound. As it died it started to make a spinning noise, that lasted a couple of months. Now the noise is gone and I'm sure it's gone. And I'm pretty sure thats why it's been blowing that black smoke like it does on the up side of hills.

UPDATE:
The reason my turbo wasn't working is because the vacuum pump was bad. It now seems to be working fine.

Just got my vac pump replaced. No smoke!!!

make sure the exhaust actuator hose is hooked up it is located under the turbo housing