Get a diagnostic test 1st and it may point to the TPS sensor and pigtail. Some things to check before spending alot of $ is the "Buick Forum" which helped me out alot. Replace the fuel pump relay, fuel pump fuse, coil packs, have ICM module tested, check the fire on the front (3plugs). If you need a fuel pump only get AC Delco. (also put daelectric grease on the connectors where the pump hooks up) Pay it forward. I was able to go back to the repair shop and get a full refund of the service that they had provided because of a faulty part (TPS). Beware of faulty parts if recently replaced. Hope this help.