well i went down to edge and got the correct harness for the 01-03 so now i have both of them. yes you can change it on the fly on the top setting it is like 75 hp not to much, iam still running my stock transmission and it is working great, i was running both the TS performance chip stacked with the juice attitude but i am going to go a different route with my truck. i have had it on my truck for just over a year and dont have a complaint one about it, i dont know right off hand what the power levels are on it i would go from the stock setting to the extreme setting thats all i ever used, hope i answered all of your questions,