Engine Performance on Cold Start Concern

The first time it happened it was colder and it had been raining a lot too. That's what led me to bench test the box. I always run and drive the car for a good 30-45 min whenever I start it up. Gas has been getting worse here too which I'm sure doesn't help. Every few tanks I put in a couple of gallons of 110 leaded racing fuel plus I've put in a couple ounces of that Sta-Bil 'anti-ethanol' additive recently to help offset the poor quality. I also put new needle/seat assemblies and accelerator pump in. Was thinking to put new plugs in too so I'll do that next. Thanks