Anyone run high-flow Cats to reduce hydrocarbon exhaust smell?

We had to run high flow cats on our rally cars in SCCA for a year or 2. No power-robbing effect was noticed on our 250-275 HP boosted 2.6L engine.

But here is what is mystifying me in this whole situation. Why run 14.5 AFR at idle? It is absolutely normal to run higher (leaner) AFR's under idle and light loading conditions. Is a fixed AFR a limitation the computer or carb begin used here? I guess am missing some info here.....