Hi Doc Here
I Don't know about on a Jag, But my vette Has a Plate between the EGR and the Manifold, about 1/2 inch thick...Requires 3 gaskets to put it all together, and is a bear to seal, but once it's all good, everything fits KEWL....
Trick is to get a Replacement Valve with proper Shaft travel with the new spacer...
If you run a block plate.... (My Road Doggie "MURPHY " is lookin' for another style ride to be an "A" driver for..glad to get rid of him...) You'll undoubtedly get the "Ominous" Two year Summons From the Department Of Monsters and Vampires ... To Stand and Submit ....
Smog Check 2 ... (Not just a Job ... an Adventure) ... Toughest Standards going ... I refer to my 12 Referee Visits, 11 Failed tests ... $6100.00 in parts (I really didn't want... don't make it go any faster....what good is it?) and a "Partridge in a pear Tree" ... I was allowed to once again "Road" My Vette...(which was never built for Ca Smog anyway..)
So If you run the Plate, Save it and the Old Valve Cover...CUZ your Going to have to have it to Pass The BAR (Not related to Becoming an attorney Or Getting Drunk ... but should be...) Bureau Of Automotive Repair ... Cuz during the Visual ... they might notice the Vacancy and I think the Confuser Program looks for it too.
California .. Land Of Smog and Hogs...(2 wheel types)