If you read the first post it clearly says the guy with the Upsolute chip who dynoed it got a gain of 9hp at the rear wheels. So Renntech would be right there. I just think overall they are a much more well known brand name.. so they aren't going to do anything to ruin our cars.. or their reputation as a premier mercedes tuner.. and their #s are probably conservative to be on the safe side. I just trust them more and I rather pay $1000 than $400 from a brand nobody has heard of. Who knows if Upsolute chips are slowly ruining guys cars? I sure hope not but we won't know for some time. Cmon its the same thing as buying an xfire with 215 hp or a hyundai tiberon with 215hp and the same exact options.. One is just a better brand than the other, even though the hp is the same, and they both have leather, etc etc.