It gives you the ability to go over the top of the airbox and more importantly be able to get extra clearance to lift the whole works over the fan section of the shroud. You gain 4 to 6” of extra height doing the partial drop.

@joe912/62

If you get to the point of lifting the whole works off and out, a partial drop will give you more clearance as rwest said. As far as the runner nuts and washer removal goes, I find it easier on the back to remove these without the drop. However, (flogging a dead horse here maybe) #6 runner might require a drop unless you have a really good set of tools: good 1/4" drive ratchet and swivel sockets of just the right size (smaller the better for 12mm) and extension assortment. You might find , not enough room to work the ratchet in the confines of number 6 without a drop.

The back components are really the front ones? The bolt holding the bracket to the "front" of the air-box can be reached more easily with a partial drop as you can go over the throttle body or top of the air-box to get at it. Might not need to drop though ... as boyt911sc said, he has likely removed more CIS stuff than most.

Airbox nut
 

Here is a picture of the nuts (nut) to remove off the front of the air-box. Looks like after the heater fan bracket is removed you might reach it without a drop. Oh and this picture shows that pesky spring which also hooks on number 2 runner. Don’t lose it somewhere, mine lodged in my dilapidated engine pad, took me a long time to find it.



http://forums.pelicanparts.com/uploa...1667649269.jpg

It would have been awesome if Porsche had put removable access panels in the rear back
of the seats.

Can I remove this in the car to get better access to runner #6?http://forums.pelicanparts.com/uploa...1667671806.JPG

You can, but suggest you should try to access the inner #6 without removing the AAV.
You need to unplug the AAV (electrical plug) to remove the whose CIS unit, not clear removing the AAV unit now helps you get the runner nuts off number 6.

Access the inner nut from the top of the oil filter fan tunnel. This takes good tools and or a partial drop to help with room to move the ratchet.

Good luck

I noticed the deceleration valve is blocked off, should it?
If not where does it connect to? It seems it should connect to a T fitting going to the throttle housing. I have an 82 SC

No clue on the decel hookup. However, decel position looks like it’s going to make getting runner 6 off and back on in SITU a real challenge. Do some research on the forum. Some of the folks claiming rapid times are speaking of 78 and 77 CIS. These, are tough enough, but yours looks really tough with the Decel there.

Maybe do some research and see who/how have done an 82 in SITU. Maybe Tony has?

The decel valve keeps the RPM up after letting off the throttle so the driver has more time to shift without the RPM dropping off. Plugging the vacuum line just keeps that valve closed so that the RPM drop more quickly but it causes no other downsides (or if you want fast shifts plug it anyway). The diaphragm in there probably broke at some point (like mine) and a previous owner plugged it instead of replacing it. When it fails it lets too much air through and the RPM go up up up.

This shows the vacuum connection (item 13) back to the throttle body. If you have cruise control its on the same tee connector as the line to the CC module.

https://jimsbasementworkshop.com/CIS...nes'80.jpg

I do have cruise control but it's unplugged so I disconnected it at the cruise control and attached it to the valve, haven't tried it but I found when I came to a stop the RPM really drop and then come back to normal, wondering if that's the issue.

That sounds like a different issue. The line to cruise control should have a tee in it that goes to the decel valve, make sure that, if the tee is there, the other end is plugged.

No Tee there it was just connected directly to the cruise and the valve was plugged.
Sh I leave it as it was?

The tee is (or should be) right next to the throttle body.

I bought a T and short section of hose

Went for a short drive and did notice a higher maintained RPM when shifting gears.

Is this the tube that needs to be plugged? Pull off the black tube put a tee into the tube and also plug the little metal nipple on the decel device?

http://forums.pelicanparts.com/uploa...1668964530.jpg

I'd rather drop the engine.

The decel valve is there for emissions- cis = constant fuel - on decel too much fuel and can harm cat converter. So decel valve slows down engine deceleration by letting in air after throttle snaps shut. This results in a more controlled af ratio on decel. Plugging it allows engine to slow quicker, and also introduces a few pops and bangs to the exhaust note. No other effect, although maybe it does harm the cat or spike nox momentarily. Obv if you have a cat bypass pipe in a non emissions location it’s unnecessary.

As noted when they fail they will increase idle up to 2000 rpm by letting in extra air around the throttle.

You don't need to plug the port on the valve body itself--without vacuum it does nothing. You just need to plug the line from the throttle body.

Mine was plugged and the line from the throttle body was connect to the cruise control unit which hasn't worked since I bought the car 2 years ago. I bought a tee connector and ran a line to the decel valve.