Of course the poor cold running could be any one of a number of things but since you already suspect a need for injector service here's how I'd go about tracking things down---1st step would be to get a fuel pressure reading from cold to warm. Your CPR supplies a richer mixture during warm-up and does that by regulating the fuel pressure. The richer mixture works in combination with the air slide valve which provides a higher warm-up idle speed. You'll want to confirm that the air slide works and that line pressure, warm-up pressures and hot running pressure are correct. After warm-up spritz water around the injectors to check for injector seal leakage (vacuum leak) and around the bellows and intake manifold. If you've ever witnessed the meager uneven spray of a clogged injector--compared to the nice spray of a cleaned/rebuilt one--you'd wonder how the motor ever ran at all. Many carburetor shops now offer reasonable prices for injector cleaning--especially for the simple K-jet type. Leak down of fuel could cause your afternoon starting issues. K-jet is really a simple system--but does require tests to deternmine what works and what doesn't. You can fix it by chasing a parts list like a dog chasing its tail. You may catch it right away---or not. -- Dave