It seems like the contrails are causing an FPS issue.

 

I've been using the product with no issue (granted I have not seen the rain or snow effects), and have seen the contrails in a more faint rendition (like the contrails were not as prominent because the air was warmer, maybe?), however as I cross over the northern United States where the air temperature is much colder the contrails are a lot more visible and as such are causing my sim to lose a significant amount of FPS (runs at 13fps when viewing the contrail, 30 fps when not). I noticed that when I was inside of the aircraft in the VC I would have better FPS than when I was outside and the contrail effect could be seen, which is the exact opposite of what normally tends to happen.

 

I went and checked my FSX.cfg to make sure no other addon changed any settings, and it was fine. I am left to believe it is the effect since this was never an issue prior to using them.

Unsure whether the product you're referring to is the same as I've read about some time ago, but several guys on the forums were all reporting that the contrails software had a big impact on frames.

Yeah, now I am unsure. I walked away and just came back, everything is 30 FPS. I may have been over an in development scenery from a friend that was being rendered and causing the problem.

 

False alarm? I'll just have to do some testing with it