Aircooled Dave

Yep. They have to drill the cross passages and having a flat surface instead of a cylindrical makes drilling/machining those a lot easier and more accurate. Once all the passages are drilled, the plugs are added. Very common design method when post machining is required with die-casting.

ToSi

It's even more clever than that.. the inner passages are die cast too. The tooling includes a movable slide which retracts to allow the part to be freed from its mold. The only machining is for the cut plug seat & threading the inlet / outlet ports. This is one of the reasons a typical Porsche costs $20+ per lb vs. $8 to $10 for a more mainstream brand..

here's a how-to delete thread -> https://rennlist.com/forums/993-foru...eed-plugs.html

Patrick MS doesn't show the plugs on their website anymore. Should be easy to cut / crimp / weld the existing parts if you don't plan to revert to stock. You'll need a rubber plug for the back of the airbox too.

Parts removed (from http://rennsportkc.com/1995-993-sai-system-removal/):


Now, if only someone could figure out a reliable SAI bypass circuit to fool the ECU into thinking these parts are still there. . .

Aircooled Dave

yep, a slide action is a definite possibility here. I haven't looked at one of these in detail myself, but whether the passages are drilled or cast using slide actions, the point is the same. The plugs are just used to close off those passages due to the mfg process.

Note I have a '96 C4S so getting rid of and/or bypassing this contraption at some point is high on my list of to-do's. I have the bypass circuit, but haven't installed due to no need at the moment. I've also though about ways to keep the SAI, but re-route it so it's embedded into the exhaust pipe rather than the head next to the exhaust valve with a tiny port. All modern cars use a large vacuum operated valve on the exhuast. These fail at times too, but they're relatively inexpensive and you only need 2. The plumbing is a lot more straightforward as well resulting in less potential for leaks. Would be illegal in some states due to visual, but I'm sure it would work just about the same. Granted, the head will be hotter so perhaps it's slightly more efficient to inject there, but I doubt anyone would really notice. You would be able to ditch this crazy manifold and multipel fittings with that setup for sure.