I've read some of the posts re VIS valves on the KV6. What's your experiences? A151 update is a free recall update OR another opportunity for the dealership to gorge on the blood of innocent LR owners (haven't spoken to my local dealer yet)? I think the general jist is; get the update and then replace the manifold with a Rover 75 jobbie.
I saw someone saying that the VIS valves have 2 states - OPEN or CLOSED and that A151 cycles the valves to the OPEN position, where they stay. If that is the case; can the valves not be induced to stay in the OPEN position - I've not looked into this yet, just thinking aloud.
Anyone?

A151 is a software update which is applicable to certain engine/vin numbers for recall.
Motors went too far and it caused problems.
After A151 update (if required) they would then test the vis to see if it worked. If it didn't then they needed replaced.
VIS open and close depending on the rev's.
Search you tube and you'll see them being tested.

I don't believe that the A151 updated does anything to limit VIS motor movement range as this is controlled in each VIS motor it's self by limit switches. These no way software can alter what a switch is doing. The update more likely limits current supplied to the VIS motors to reduce the chance of them burning out. The VIS motors only failed because they become oil contaminated. This is easy fixed by drilling a 0.5 mm hole in the top of each VIS motor case. This keeps the VIS motor at a lower vacuum than the plenum, so keeping the oil out.
Noise in the plenum is often caused by the power valves breaking loose from the control linkage, simply flopping about uncontrolled.

I think from memory some vis came off and got stuck or caused damage. This was a long time ago when we had major problems with them in FL's. LR seemed to solve the problem early on.
I guess the software either pulsed/drove the motors slower than normal, or was more precise when calibrating movement or detecting movement betterer. Like adding a line of code saying "if powered for more than N second then stop, as the motors gone too far and the switch may not be working, as powering for N seconds is physically too far".
v7 firmware in the Hawkeye can control vis to test them when fitted to ma hippo which is a new feature.
I have attached the bulletin I have.