I don’t understand why you’re still insisting on having the tires filled with nitrogen. Atmospheric air is mostly nitrogen. Unless your wheels have two valve stems and the shop uses an excessive amount of nitrogen, you will never get 100% of the air that was in the tire out. Nitrogen gives no benefit to passenger cars - it’s used in proper race cars to reduce pressure changes when hot. That’s hot in racing terms, where the brakes glow red hot in daylight and the tires wear out in 30 minutes from the sliding friction. Normal cars don’t get that hot, and a 1 or 2 pound difference in pressure just doesn’t matter that much.