I'm seriously considering doing this, but I have some questions.

Do I need any kind of adapter plate between the upper and lower manifolds?
Do the fuel rails need to be altered at all?
What'* the part # for the L26 UIM?

I've read alot about this over at clubgp. There'* no adapter plate needed for the lowerintake. But i think you need one for the throttlebody. I think i read somewhere that the adapterplate for the gen 5 */c works? i forgot.
Someone on gp did the install and it made it actually slower. :? It might have to do with the longer and restrictive inlet to the intake manifold. There was talk about boring it out to solve this but i'm not sure anyone did it.
The fuel rail will fit if you don't have the HVII.

I'm not sure about the part number but if you search on the L36 forum at gp i'm sure u'll find it somewheres.

Ohh yeah and if your main reason was the upperintakeleak. Then just get the HVII. It blocks the coolant ports before they come close to the EGR.
I would just want it cause it looks pretty though.

i've been working on this for about two months now, and come early october, i'll be doing this to my car, along with a full write-up, and dimensions for an adaptor plate that will allow you to keep your stock TB.

as of right now, the solutions that are being used require a new TB, typically from an L67. I have my own theories on why his car was slower, but I don't think that will be the outcome when I do it.

anyhew, if you can hold off for about a month, I should be able to answer all of those questions for you, and have a solid procedure down for the H bods to use the L26 UIM.

1. fuel rails do not need to be modified.
2. there are two part numbers - the one you'll find on clubGP, and the one that I was given by SPO. i know which one I trust more it seems that the number changed a little bit, but people ordering from gm parts direct will still prolly end up with the right part.
3. as stated above, lower intake manifold is common. you will need an adaptor for the throttle body.
4. the aluminum UIM is actually cheaper than the composite, even if you buy a third party (ie dorman) intake. so the real trick is how much you spend on the TB adaptor. if it'* cheap enough, replacing with the aluminum upper will be more economical than replacing a failed composite.

5. if you don't have one already, you will need a cai when you're done. the neck of the aluminum upper is longer and has a slightly different angle to the throttle body. throw in an adaptor, and the stock airbox is pretty close to useless.

I plan on upgrading to a Northstar TB when I do the switch, this is for another little project I plan to do next year.
So it sounds like all I really need part wise is the the UIM and adapter for the TB.

that'* pretty much it then. bolts right down to the lower, and maintains the same vaccum connections and stuff that our current one does. The only change is that the vent that goes through the lower intake manifold (did you catch that post? we were trying to figure out what a hole was for in the throttle body) currently goes to our throttle body, whereas on the L26, it just shoots straight up to a connection where it goes via vacuum line to the intake pipe. Just pulls in clean filtered air, so as long as you've got your own intake, that shouldn't be too much of a problem either. or, if the TB you're going for has that feature in it, you could work it in somehow.

Good luck you guys.
I'm really looking forward to seeing this done in an h bod.

is ther any way to port it or make it flow better?

This would be a good application for the turboed cars out ther, who know how that plastic one will hold up to added pressure and heat.

I did a search over on CGP and couldnt come up with a part number no matter what permutation I put in the search field. Can anyone tell me what it is?

this is from clubgp

89017283