New Upper Intake Manifold and Throttle Body Problem

I just installed, on my 2003 6G72 8G GTZ, a 2001 6G74 Diamante upper intake manifold and a 2001 6G74 Montero Sport throttle body (slightly bigger bore than 6G72 stock). Everything is working fine except for following codes:

1) P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

Solution: I need an EGR pipe gasket. I've ordered a new one to replace the one I've lost or never had. I've tried using Permatex but evidently unsuccessful.


2) P0507 - Idle Control System RPM Higher Than Expected

For this I've:
a) Verified the TPS placement with mechanic.
b) Adjusted throttle cable. Now has large amount of slack.
c) Throttle body was cleaned prior to install.
d) (IAC) valve should be fine. No problem with it when TB removed from my Montero.
e) There are no Intake air leaks If there were, the idle would be rough but it's smooth just a little high.

Since the TB came from a 6G74 3.5L Montero Sport, could it be that the Idle Screw needs to be adjusted. This is just a guess. What do you guys think.

Much appreciate your assistance!

Don't touch the Idle Screw, leave that alone. I don't know about the IAC on the Montero TB but the computer just needs to adjust itself after driving with the new IAC. I upgraded to the Diamante 6g74 TB and I had the same code, went away with driving the car for a week. The EGR valve on the 6g74 could be bad, I think your 6g72 EGR valve should fit the 74 IM, the nipple on it will just be in a different direction.