impedance is function of width of line (with some adjustment of copper thickness) plus thickness of prepag directly below surface where your lines are. So, you need to compare what is on your last pcb and what is on your new pcb. best software to calculate this value is polaris and you can get some days for free if you ask for code but there are free alternatives out there like Saturn that we use. Beside that there are differential lines that you also need to match impedance. I am not sure but I doubt that via registers you can fix this problem.
also, in some cases you can put resistors in series of lines where you think you have problem.