I decided to cut away at the vanes that held the original runners in place. I didn't want to go too far and harm it structurally but a good amount was taken off.
Looking through the throttlebody, the vanes did not look like they are helping flow to the furthest cylinders. The LIM runners had less carbon as you moved away from the TB too. An indication that flow through the manifold may be suffering.
I figured I would give it a shot since I doubt it could hurt anything.
Remember also that I have a HVII and will not be using the stock runners.




I'm not going to drive it till tomorrow and I'll let you knwo if there is any noticable improvement.

yes keep us posted looking forward for those result is that a stock GM upper

YES! THANK you! I was wondering if someone was gonna play with the UIM soon... I REALLY don't wanna shell out 200 bucks for an HV3 from ZZP... Can't wait for the outcome

Cool idea, Cooney... I'm definitely awaiting the results

I like the concept of modifying the original UIM to see what sort of improvements and gains can be had. I think a lot of people dismiss the L36 upper as being irreparable junk.

Firebuick, yep it'* a stock upper.

Petra, this isn't really a substitute for a HV3. I did this to help flow for my HVII. You would need the HVII or HV3 to do this.

Well guys, the butt dyno didn't see any noticable difference either way. :(

It'* a possibility that this may be a higher rpm thing. I'm only spinning to 6k right now.

I'll let you know if my fuel trims change drastically after my computer re-learns it'* self or if more power comes in later.