Difficult Starting and Idle...Spark Plug Related???

I'm just throwing out a hypothesis and you guys can let me know if you disagree or agree. This summer I changed my Spark Plugs to Autolite 24s or 23s for Nitrous. I think it was 23s which is a colder plug than stock. I also retarded the timing but I put that back to 14* because I'm not using the nitrous in the winter. Now that it is getting colder my car is starting very sluggishly if at all. The idle is also a little weird. The car seems like it is running too rich. The N/A performance is also down than with the old plugs which was expected some what. If I changed to Autolite 25s would this cure my idle problem and starting you think? Also what gap should the plugs be at for N/A. I might run two sets of plugs the 25s in the winter without nitrous then the 23s in the spring and summer with the nitrous. Any thoughts?

Don't have a code scanner and I need a new harmonic balancer so I don't want to drive it to advanced auto until I get that done. I'm hoping the balancer will cure all the problems but if it doesn't I'm just speculating different things to try that are the cheapest first. I reset the computer by unplugging the battery the other day and it does idle better. Hopefully it's just a minor problem.

Yeah I figured the faulty balancer is throwing off the timing which could cause a lot of the problems.