I used to have a HKS EVCiii. It worked well, but mine seemed to be a rare case. Since then I have switched to the Innovative Turbo boost controller and have had great success. Check out the website for more info on them.
But one thing to consider is without a functioning wastegate, any boost controller is going to be worthless. I.e if you have a stock wg with no cat. No boost controller is going to fix your problem.