I spent alot of time working on Jags, and have owned some too.
I think the old 3.8 and 4.2 litre straight six were excellent engines.
But, after I owned a 12 cylinder XJS, I was amazed at how good that engine was.
For a long time before I got one, I thought they were over-kill, and too complicated.
But after owning one for a while, and since i was already accustomed to what went wrong with them and how to fix them, I thought that 12-cyl was a magnificent engine.
I sadly lamented the end of that engine, and after that, Jag used all Ford engines in the Jags, and it was the end for Jaguar.
For any Jag enthusiast, the XJS is a superb car, and a bargain on the used market.
They do take alot of maintenance, and will cost alot for parts, but once you get into them and know how they tick, they are not hard to work on, and are remarkably good engines.
I loved mine,which was a 1988 roadster, converted from a hardtop by some company in FL, before Jag began making the convertible in 1989.
You'll never drive anything smoother than that car. It's awesome. And the power delivery is really nice. Has a GM auto trans, so tranny work is no problem, but mine never needed any. The rear suspension is exactly the same as the old E-type, and the front uses coil springs and does away with that old torsion bar setup that the E-type had. It handled great.
Loved it.
I had it until a giant tree fell onto it in the yard, and crushed it like an egg. That was a sad day.
Regarding the SAAB, I worked on them during the late 1970s, when the 99E was just beginning.
That 99E engine was a piece of shit.
The Triumph TR7 had the same engine in it. POS.
My favorite SAAB was the Sonnet III sports coupe.