In addition to what has already been mentioned I would say the injectors themselves may be due for an overhaul.

Shifted
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'87 745t 214,000; '93 Toyota MkII; '73 Suzuki Jimny (Brute) LJ20 360cc

if you had a bmw, i'd say start with the valve adjustment first. a volvo-nah. i've checked probably 50 or so cars and have adjusted 3 valves total. 1 car had a loud tick, so it was easy to tell it needed a valve adj. the other changed to a k cam and he got 2 shims. unless you have a loud tick under the valve cover, i would look elsewhere for the miss.

all the new items SHOULD be-bosch or ngk plugs, no platinums, ever. bosch cap and rotor, but NOT wires. those should be bougicord or oe only, nothing else will do. i've had customers do their own tuneup and use the cheapest parts on sale, then bring it to the shop 'cuz it wasn't right. many a time, i've just installed the right stuff and the car was happy. i've also had bosch wires bite me right out of the box, bad coil wire, etc. if that's ok, then look for vacuum leaks and run some injector cleaner through it. good luck, chuck.

I would suspect a leaky injector seal or vacuum leak first. Have you done a compression check on all cylinders? This will give you some indications as to the health of your valves & rings.

Good luck
Danny Mac