I’m confused. Are you saying you still have this problem but you fixed it? If you fixed it you wouldn’t have the problem anymore.

If it is fixed then I agree that your issue is with the FBC since a MBC fixed the problem but when I had this problem it was just a vac leak. I’m glad I didn’t go out and spend $100 (or whatever it costs) on a new MBC or FBC since it ended up being a $1 piece of vac hose.

Are you talking about your problem or yours along with all of the others in this thread?

You're saying that you have a boost spike problem and it has nothing to do with boost spike.

What's your definition of boost spike and what problem were you having?

I'm not trying to be an a$$, I'm just a little confused by your post

 

Sorry for the confusion. Let me try to clarify because it's possible my problem is different. When I moved from UTEC back to the stock ECU, I immediately had problems with boost (moving back meant uninstalling the Auxillary boost controller that came with it). The boost gauge would swing to about 13.5psi, then down to about 6, then back up to 13.5psi, then back down over and over. I wasn't seeing spikes per say, as it was never sitting at peak boost for longer than a half second, if that.

I have always looked at spiking as sudden jumps above your desired peak boost. This is more of a problem with the FBC not holding boost.

If I go back to the FBC, then the problem is still there. So I "fixed" it by using an MBC that I built using about $7 worth or parts bought at Home Depot. I would never pay more than that for one, and this one works very well. I did check all of my vaccum hoses (about 20 times because I was so irritated by it) and never found one that was disconnected, cracked or perforated. That said, I might have completely missed a hole or crack somewhere that wasn't easy to find. I wanted to make sure the wastegate wasn't having issues, and the MBC showed that it wasn't. My conclusion was the FBC, which could very well be wrong. I just reinstalled a UTEC tonight, but haven't had any chance to put the auxillary boost controller in and see if it will all work like it did before. Wish me luck.

As for the others in this thread, I think they are having the same issue because their descriptions sound similar.

If it turns out that my case is completely isolated, then by all means ignore it, and I'm sorry for wasting anyone's time.

 

You’re not wasting anyone’s time at all especially if you hook these guys up with a way to build a MBC for $7. That would be a good, cheap way to find out if their FBC is bad. The troubleshooting I mentioned only tells you if the WG is functioning properly and it can be a pain in the a$$ to find someone to lend you a FBC for a test run. Your $7 MBC could be a very helpful troubleshooting tool.

It does sound like your problem is a bit different since these guys are over boosting at around 16psi which is 2.5ish psi over the ecu’s target and yours is dropping after the ecu sees target boost.

Good luck with the UTEC install.

 

Wow, I come back to i-club a few months later and all these replies. Thank you all for the advice, but still the same problem. I've resorted to running a mbc set at factory boost levels. I guess I really can't complain, but I do hate the partial throttle, full boost. I see I'm definitley not the only one with this problem, and that an accessport won't help me in this matter. I drove my friends 06' sti a week ago, and he has the same mods as I do. Amazing...no lag at almost any rpm and holds boost strong and steady. Not to mention a hell of a lot faster. For me, I'm sold. The 2.5 is great, and I plan on getting an 04' sti in the near future. Problem solved.