Longer runners give you more low end power, and shorter runners give you more high end power. The HV3 should have shorter runners, but I talked to ZZP about it over the phone and they were kind of unclear on the design and even stated that it'* bigger than OE. I think holes cut into the UIM insert would work really well with a better flowing throttle body to help to up the manifold pressure.
Overall, I believe we should have even longer runners. The 3800 intake manifold seems to be very small in comparison to other manfiolds, and shortening the runners even more may work against where the 3800'* true power lies. It'* not that it'* bad for the engine, but you're simply shifting the power band to an RPM range that may not feel ideal.
From talking on the phone and in person with a few people who have 400 & 500 HP 3800s, places like PRJ Performance and ZZP, I am still unsure about if the effects of the HV3. Ultimately, I think it'* unnecessary. That being said, I assure you that cutting holes in the insert will change something for the better. What exactly is changed isn't clear to me, and that'* why you can experiment if you want. Your engine will behave differently, and you will likely have more power higher up in the RPM range.
Looking over all that, I may not have clarified ideally. Please let me know if anything else seems confusing.
94 STEi and 99 SLO