I agree, that's far too many repairs for what appears to be a air leak on one side. The dealers have a general practice of throwing parts at the car and hoping that that the problem is fixed, especially with out of warranty cars.
Find an independent foreign car specialist and ask them to do a smoke test.

 

Have you replaced the MAS unit? I tried 3 rebuilt ones from NAPA and they worked great except at idle after warm they would trigger the restricted performance notice which would go away upon acceleration. It was a PIA to me so I just cleaned and re-installed the old one.

 

help i get a restricted performance on a xjr 99

 

You will get more assistance if you open a new thread instead of hijacking an existing one.

But not much assistance can be offered until you get the stored codes read. You local auto stores will read them for free, but you should consider buying a code reader of your own. Come back with the actual codes, not the code readers interpretation.

Please visit the new member area and introduce yourself and your car:

New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

 

I just noticed you have a XJR. This is the XK8/XKR forum. You should post on the X308 forum.

 

Final follow up. I got sick of trying to diagnose this myself and decided to take it in to Jaguar. It ended up being a dirty MAF sensor. This is very interesting since I'm not sure what they did differently than my cleaning, but the car drives better than it has for years I thought it had lost a few ponies with age, but she feels young and eager once more.