Thanks. I’m afraid to look, though - if I see anyone I know there I might want to slap them silly … Who the heck would want an XJS w/o the V-12 engine (or at least the 4.0), despite the “problems” that may come with it? 
Sorta like making a cake and leaving any frosting off of it … (I know, maybe that’s not a good analogy 
) …
I agree with ya there, Equip. ^5
Hello AttyDall - I get the “cake no frosting” joke - personally I prefer the V12, but I understand that some owners want the “style” of the Jaguar, but prefer to maintain another engine instead of the V12 for many different reasons, hence the “Lumps” section - there used to be a fellow, out of the Dallas area, that sold kits to help with the conversion, such as engine mounts and bell housing conversions - not sure about what else, such as harness etc. - think it was called John’s Quarterbreed - mostly for installing a Small Block Chevy (SBC) in to the XJS - don’t think he is still doing these kits, but not sure - Tex Terry, II - 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - sent 11/19/2020 0040hrs. EST USA.
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Yep, that’s “John John”. I really miss his servicing Jags, but he made the decision several years ago to discontinue that part of his biz … (no mention as to why) … 
He does still sell parts off his “dead herd” of Jags out front (one of which are the remains of my beloved Supercat - black/black '95 4.0 coupe 
), but I’m thinking most of his money these days does come off sales of his lump conversion kit he developed a long time ago … 
But it’s not John_john1, a current contributor to these forums and producer of several excellent machined parts for our Jags.
Yes, don’t want to get them confused … John’s Cars = our local “John John” … Thanks for clarifying that, Palmdude … 
Sorry, I wasn’t clear. I know the XJR-S has the Zytek ECU as well, since I have a 1992 model. I was using TWR as a generic term for the engine management system that they developed and was then taken up by JaguarSport.
Each time my XJR-S starts I breath a sigh of relief. But I didn’t think the distributor was particularly special - just a stripped out Lucas unit.
Actually, the wife’s '92 5.3 V12 has a 26CU…
Thanks for all the feed back guys,
So I managed to get my hands on a AJ6 engineering adjustable 6CU. It has the following on the body of the ECU:-
000 = - 32%
416 = STD
999 = + 45%
can someone tell me what these number relate to? Its current set at 462 and this number has been written next to the adjustable pot…
I found out recently l have the 3CU (for D Jetronic) which is followed by the 8CU and 16CU finishing with the 32CU which l guess was for the Marelli? 8 and 16 were both compatible and used with the ‘P’ Injection