About spark plug gaps it's the gap/distance between the center and the side electrode that you measuring and adjust by bending the side electrode so you get the prefered value (you have to take the spark plugs out to do this).
- Does that mean the larger electrode gaps don't need checking?
I don't understand this, what are you meaning ?
- Faulty pinging sensors - can this be checked, if not is it easy to replace and how much?
Yes by using diagnostic tool or measure the resistance of the pinging sensor (but be aware that Ohm measure not always tell the truth about the sensor, it can change behavior when it is varm), it is a bit of digging down to them before you can replace them, they are not to
expencive but i can't remember how much.
But i don't think you have problem with them as you only have hesitation when you is throttling fully (or els you probably would have some erratic engine behavior even when you are not throttling hard).
- I put 95 Rating fuel in the car.
It's fine, but the engin runs a littel bit better on 96 or 98, but at least my car doesn't like Shell V-power (99) for some mysterious reason.
- Can the petrol filter be checked to see if it is clogged?
No, at least not esaly, the filter is not expensive, just change it if you don't know how old it is, it is mounted on the rear right hand side underneath the car (observe the arrow printed on the filter, so that the new one is pointing in the same direction as the old one)
- FPR - can that be checked easily?
You need to connect a fuel pressure gauge in line with fuel rail to make some readings, easy or not ? you decide.
- I don't even want to go into the air leak scenario.
If you don't have tools to pressurise the intake system then you have to go visual, looking for loos hose clamps, cracked hoses etc. and signs off any leak, on my car the OE hose clamps on the rubber tubes connecting intake plenum with intake runners didn't manage the pressure and i did have some traces off air leak on the intake runners (an oily residue) changing clamps to ones with screw sorted that.
I still think you should start with the spark plug gaps.