the motordyne Art pipes are test pipes with a hemholz (sp?) resonator so they don't give that raspy, sh!tty sound that a "regular" test pipe does. Apparently, they're even better than your normal resonated TPs as well. Seem to also pick up a couple hp over all the other TPs to boot.

No way of knowing if it's safe or not to drive around w/o an updated tune to account for the TPs w/o knowing a/f ratios, but if it were me (and I'd throw your bud's tp's on asap just to get those sh!tty HFCs outta there), I'd just keep it under 4K rpms and no heavy throttle until I could get the car on the dyno and retuned. If you got tuned originally at HP logic, I believe they offer a significant discount when you come back for retunes, so hopefully you won't be out of pocket too much more $$.

^My vote.

Your buddy in the white Z was interested in the test pipe as well. When you're done with them, just sell them to him haha

OR

I believe Motordyne has some ART pipes in stock from the same batch that they shipped mine. They sell very quickly.