Will changing the belt length and idler pully sizes change the boost or output on an Eaton?

Basically, the Eaton M90 kit I have on my Explorer was made for a different 302 setup that Explorers had (heads were different, EGR setup was different, etc). The kit mounted the same on my 302 setup, but something was different about the pully setup. The belt routing is the same, but when I put it on by the instructions, it pulled the tensioner fully. I didn't want to burn any bearings, etc, so I changed out to smaller idler pullies and used a longer belt to create some slack on the tensioner. Will this make a difference on output? My initial thoughts are not because I am still turning the same rpm, etc, but I don't know for sure. Any thoughts?

 

It shouldn't, the idler pulleys are just there to keep tension on the belt, they have no reflection on the RPM of the belt.

 

No it won't, as the ratio from the drive pulley to the driven pulley is the same.
The only thing you have to make sure about is that you still have enough tension on longer belt to ensure the belt isn't slipping, and therefore causing a lower amount of boost than would otherwise be expected..