what would be the best intake for 95 C2500 TBI with XE 256 H from comp cams coustom tune for that cam and headers?

 

WHAT HEADS?

There are VERY few choices if you intend to keep the EGR functional.

I used "old style" 6-bolt heads where all the intake manifold bolt holes are at the same angle--not TBI heads where the center two are more upright. Then I installed a "ZZ4" style intake manifold which is the same height as the original TBI manifold. A thin TBI adapter plate was needed, along with a purchased EGR adapter, and a second adapter I had to fabricate from thin steel plate. The vacuum tube to the brake booster had to be cut, bent, and re-routed, and I had to make a small adapter to fit the OEM coil onto the intake manifold. Also had to adapt the heater outlet fitting to the ZZ manifold.

I looked at using the stock TBI manifold and ovaling the center two bolt holes on each side--but this did not seem possible to me. The TBI manifold has hollowed-out areas around the bolt holes on the underside, and I'd have to grind into one of the hollows which leaves no strength.

Vortec heads need the GM-TBI-Vortec intake manifold which is hugely expensive, and you still have to buy the EGR hardware to route exhaust gas from the exhaust manifold or header to the intake manifold. That's well over a hundred dollars for the tube and various fittings.

If you're using the TBI heads, I think you're stuck with the original manifold. The aftermarket manifolds by Holley and Edelbrock each have their own problems.

Photos of my "ZZ" manifold and TBI system:

Purchased adapter to move EGR behind IAC valve


Adapting TBI EGR to purchased EGR adapter.



Homemade adapter plate for EGR


Brass 45 degree street elbow, short brass pipe-thread nipple, and Dorman heater hose quick-connector threaded internally for 3/8 pipe thread. Manifold is already threaded.


Rear view of heater fitting.


Since I did NOT use the TBI manifold, I didn't use the "special" TBI intake gaskets that block the coolant port on the heads.

 

the new chip will disable the egr wanting to use a 4 barrel intake with adapter plate

 

If EGR is not a concern, you have the choice of any intake manifold that bolts to the heads (and works in the RPM range you're using in your application.) You'll want to give some consideration to the location and number of coolant passage threaded ports, for temp senders and the heater-core supply. And also there are bolt bosses needed for the alternator and A/C compressor brackets. The ZZ manifold I used has the boss for the alternator bracket, but not for the A/C compressor bracket.

WHAT HEADS?

Again, if you're using the goofy-bolt-angle TBI heads, your choices are pretty limited. I'm not sure there's much point to going to an aftermarket manifold considering the very limited RPM range of those heads.

If you're using the older-style 6-bolt with the bolts all at the same angle, you've got dozens if not hundreds of manifolds to choose from.

If you're using Vortec heads, you have a few choices from the "big names" as well as the Communist knock-offs from the bottom-feeders.

As for the TBI spacer on top of the 4-barrel manifold, be aware that some put the TBI unit farther forward than others. When I was looking for one, there were spacers that provided forward, center, and rearward positions for the TBI on the intake plenum. It'll make a difference in your throttle cable and trans TV valve cable adjustment. It'll also change fuel distribution within the manifold, but without testing each one you won't know if the one you select is optimum.

I used the Trans-Dapt 2211. "spread-bore, center mount". I had to change the adjustment of the TV cable quite a bit, I had very harsh shifts before I re-adjusted. The plate is steel, and threaded for the TBI hold-down bolts.
https://www.summitracing.com/parts/trd-2211
A forward-mount would provide more clearance for the EGR valve, rearward might be a problem between the EGR and the IAC. If you have no EGR, that's not an issue.

A person could make their own from a sheet of aluminum or steel, put the TBI wherever they wanted. If you used aluminum, you'd want some sort of thread reinforcement so the aluminum threads didn't pull out.