Hello,
With CIS, removing the oil cap should cause the idle to drop slightly. If it dies or stalls, it could be a sign of a too lean mixture.
With CIS, it is a good idea to get gauges and work through it methodically, otherwise you are just throwing expensive parts at it and hoping.
Here’s a very good thread
http://forums.pelicanparts.com/porsche-911-technical-forum/758788-cis-troubleshooting-dummies.html
Likely that when the shop repaired other issues, the new ones popped up because someone had applied a “band aid” fix earlier and now it needs something else corrected.