Sorry about the quality of the pic...

I mean the steel disc/valve....held into the coil body by the 5mm stainless bolt....i have several spare discs in the workshop....£22 incl p & p

Normal idling with a modified valve aint affected, once the engine is warm that is lol...the disc/valve blocks off the enlarged port in the throttle body to prevent any unwanted air passing at idle....

The downside of this set-up is reliabilty, they do require significant maintenance if you use the lag frequently...we regularly clean the valve with brake cleaner to prevent fouling....

The coil itself is a little undersized for the modified disc/valve and you may find after a while it doesn't lift properly.

We have tried for some time to find a decent alternative, not come across anything as yet.....

I personally would only use ALS on a competition car and really only a rally car as in most other situations you could drive round the lag problems....

ALS doesn't destroy lambda's, well not immediatly anyway, we have pectels own w/b in at all times.

I'm not a tuner so I cant help with the reason they use 90% valve duty..

HTH

Ian