Leads in good condition is a definite yes as they can deteriorate with age and the spark die back a bit.I replaced mine on the 4/4 as they were originals to the car and it was 20 yrs old when I bought the car. I put standard ones on and noticed a slight difference.
The “word on the street” is that Magnecor are very good. My current car had them when bought ( many thanks to a previous owner).
My view is.....
Good plugs, leads, coil( packs) plus injectors that give a good spray pattern results in a good burn.
Sorry I can’t help with a proper comparison but perhaps the racers on TM can chip in on Magnecor.
