Last week I fitted new pluigs and leads to my 2.5 110k mile Legacy. Is it just me or would this make the car run better and seem to have more get up and go? I am assuming the new plugs and wires are giving me better/ more efficient combustion - or am I just imagining the whole thing?

Not your imagination, a good tune up with new plugs and wires most certainly will pep up your car.

especailly if your plugs were worn down enough to open the gap larger than spec., which would not allow full burn of fuel, and not as strong spark...

 

Of course, new plugs, properly gapped, should increase all around performance.