The idle jets are metering jets, not a shutoff valve. Grooving in the brass needle is not going to affect the ability to meter unless it is severe. If he believes the grooves are severe he should smooth them with a piece of emery paper and go on. The idle jet adjustment process is fairly rough, and as the name says only affects idle, and if set too lean maybe the transition to mid-range. In all my years rebuilding carbs I never put in a new idle jet. Just my opinion and $0.02 - others may disagree....