The choice for which one to get first is up to you and really does not make that much of a difference.

Say you get the intake first - the tuck breathes better but can't breath it out fast enough due to same restriction in stock exhaust. However, still better than stock but not to full potential.

Say you get the exhaust first - it can exhale betteter reducing the backpressure a little but your intake is still restricted so it can't open the lungs fully, so to speak; still not to full potential.

Get whatever you like first or whatever you have the cash for.