Do you mean a cupra r splitter to the valance? Iv done it and then taken it off as it looks stupid. It looks cool on mk5 front bumpers though MK4's I would stick a splitter on the R line bumper only but thats my opinion.
adjustable front splitter
i feel bad after that reply and the wife gave me sh!t for being a twit but its personal choice mate and think the lcr splitter should only be used on the r32 front or the slcr anything else just dont look very good as for the adjustable splitter again its upto you as its your car but personally small subtle mods make the car look better imo