Warranty work depends on the individual dealer. A code three pulley will show higher then normal boost tables in the ecu, and will be as much of a problem as a 178,181 or 185.Even a tune if you open up the tables in the ecu will show the changes in calabrations. If your gonna play then you take your chances. Also the Magnuson-Moss Warranty Act (P.L. 93-637) doesn't do crap for you. The dealer will deny warranty if they so desire and you and the lawyer you have to hire will have the legal responsibility to prove them wrong
Everyone on here is smart enough to realize you always increase the chance to have you warranty denied if you alter anything from stock. Guys with the Ford 6.4 turbo diesels have had warranties denied because they used K&N filters and triggered emission controls that effect the DPF