There is a differential in the final drive gearing between the front and rear on the freelander this is blamed for the VCU failure. Running with smaller (worn) tyres on the back exaggerates this differential and can cause noticeable problems like odd noises. I bought mine cheap because the 'VCU was on the way out' but simply swapping tyres/wheels which had been fitted 'new on the front' to new on the back solved the problem and it did 70 K without issue before I took the rear prop off because a UJ failed.
Removing a blocked air filter then replacing it will probably/possibly improve air flow because you dislodge some of the muck on the element. Replacing it altogether will obviously improve air flow. Messing with tyres will not affect the performance in a straight line unless you fit noticeably different diameters ie up the gearing or reduce it.
I liked my freelander when I had it and it never let me down , even got me home when the HG failed at 215K. But it is important that owners understand what is going on and for gods sake don't listen to a garage without checking on here.
not a bad idea to air on the side of caution with tyres on an FL.
