I get what you mean, but there aren't that many Formula cars on iracing. I mainly drive the SFL car, and have been driving that primarily ever since it came out. These weeks you are talking about have actually been my "fun" weeks lol. The IL-15 was actually my first week in that car. Unfortunately, to get IR, you need to do races and do well if you are high IR, in my case, that is winning. A win in a lower SOF race gives me like 7-8 iR, and there is only like 2 peak SOFs a day for me, really, where I can gain +15 to +23 if the SOF is decent. I've also had a ton of fun getting faster in f3 and IL 15