Depends really - OEM bits are up to the job. Loads use them with no issues. Saying that ..... I've noticed some lag on my car recently when boosting then lifting off and even when changing gear. It's no major concern, car still works fine but the slightest thing bothers me If the cars not running to it's full potential. If you've got the cash it will do no harm to have them and get them fitted and set up at the same time as the map. Just the same as theres no harm in keeping the OEM bits.