I am currently only running the Eurocharged smaller supercharged pulley with the belt wrap kit and 3 Piece ASP Idler Pulley Kit

Here is my troubles,
The first belt i had was the gates K080530 (53 1/2) my mechanic said it was too small, researched on here and found out i needed about 4 more inches in length over the stock belt (which is about 51 inches). So i had shardul send me the gates K080550 (55 3/4). i got it installed but my mechanic said that now my tensioner pulley is maxing out, saying the belt works but is a tad long.

My question is do i keep running this belt or is this robbing me from a little power?

And my research shows that there are to belts available from gates between those 2 sizes and they are gates K080537 (54 1/4) and gates K080545 (55 1/8)

I think replacing the K080550 is the best thing to do, but which belt would be best? the K080537 or K080545?

It sounds like you may have a 168mm or 172mm crank pulley on your car, as all the BWK kits set up the same based on crank pulley / SC pulley sizes. Can you measure the front ring of your crank pulley and maybe take a picture? Then PM me and I can tell you the exact size you need for your set up. If you have a 168mm ring, then the K080545 may still be to long.