BajamanCam

If the ECU is given an incorrect map (causing boost controller to go nuts), this can cause knocking with a manual boost controller can't it, as the air/fuel ratio will be fluctuating as well? I think I need to take a roady somewhere for it to get logged, may get expensive!

Taupo mate. Both solenoids open and close perfectly with no air leaks on a 9V battery, unsure what they'll be like under normal conditions though, as they do pulse. Still, the chances of both being dud and having the exact same issue, yet work fine off a 9V seems highly unlikely. I'm wondering if the ECU has been played with before I took ownership, and not knowing about it? Has to be an electrical issue, seen as that a manual tap works fine? Unfortunately with me being in Taupo, there's no one close (that I know of) that can log my ECU.

Thanks for the welcome! I thought the standard boost solenoid as well, but I replaced it with an identical one and the same issue, so can't be? I've read many other forums with a similar issue and it's always the same answer - boost solenoid. But that doesn't seem to be my issue in this case, unless I bought an equally dud solenoid.

Hey ClubSub! New member here, with an issue that me and Google can't solve by ourselves. I'll try keep it short. My STi fluctuates it's boost, under WOT between 15-20psi - up, down, up, down, up, down... until I let off the gas. Occasionally it boost spikes to over 20psi before I can react and take my foot out. Car details: - Stock. Yep. What I've checked/replaced: - Checked wastegate, opens smoothly at 8(ish)psi - New vacuum lines and boost pill (all in correct place, I've looked at many different diagrams over and over again) - New boost solenoid - Checked for leaks in intercooler and hoses The thing that's really digging at me, is that it has always had a manual boost controller and held steady boost fine at 18psi. I don't like mbc's and decided to safely go back to the stock boost control system. So why is it holding boost fine with a mbc, and not the stock set-up... even though I seemed to have gone over everything? Any help appreciated. Cam