If you live in the US your car only has 181HP with "stump pulling" torque at low RPMs. You'll need to change the cams to the old style to get back to 204HP.

I use the plugs from the dealer with the multiple side electrodes and just install as supplied. Gaps are quite large, more that .03"! Have about 60K miles on the present set.

You can relieve the pressure at two places on the car. There is a port down by the filter and there is the test port on the fuel rail. There will still be pressure in the system when the engine quits using your method.

Be sure to get new copper washers to put on the "Banjo" bolt at the front of the filter and at the adapter at the back. If you put a wrench on the back of the filter you can first undo the front banjo fitting. Then you can loosen and "spin" the filter off the adapter on the back whiout having to loosen the adapter's connection to the fuel line there.

No pollen filters on this car.

I use 100% Volvo coolant in my car now. I had a head gasket let go that I think was initiated by the PO's use of "any old stuff". I would flush and change the coolant "NOW"!
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'96 965, 16' wheels, rear 18mm bar & Koni + 204HP cams at 125K. Had '85 745 Turbo Diesel for 200K.