Oh, I remember that issue.

There are two versions of that particular manifold, EFI and carb.

Both versions are (or at least, were) machined for OEM stock 5.7 O ring style gaskets.

About two years after crate engines that used that intake started selling, through customer feedback, MP found certain blends of gas, with the carbureted versions of the intake, would "swell up" the O rings over very long term use.

Subsequent contact with the "intake gasket guy" at Chrysler proper + the OE supplier for the O rings confirmed: They are not intended for long term exposure to liquid gasoline. Short term and vapor is OK.

By then, another crate engine had been released, with the predecessor to the tall DP intake on it. It did not have the O ring machining....That engine had pink fiber gaskets. Spoke with engineer for that program, he knew what the deal was. There were similar 5.7 fiber gaskets set up in the product line "just in case".

At the time it would have been damn near impossible...like an act of Congress....to change the machining on the intake. Requiring a new blueprint, PPAP, and all that "OEM" stuff that most other folks who make intakes don't have to deal with... Chrysler was bankrupt at the time, and the only reasonable solution was to recommend fiber gaskets and leave the machining alone. So that's how it happened.

You actually "can" use the O rings over the short term, and it will run just fine for you, but over time they will break down and swell up...it kind of depends on how often you run it and other factors. Although they were intended for a "dry" manifold, they can handle fuel for awhile.

BTW the big threaded hole in front is where the oil goes, there's no water in a Gen3 intake.