Saturday, I did a sea foam treatment. The smoke was unbelievable. After running that through the system, I decided to do a little more work to find my boost leak. I had Ultrik intercooler bellows on the car. I removed these and the intercooler only to discover that the vacuum connector for the boost gauge was completely dry rotted. I knew then why my boost gauge was only registering around 8 psi even at WOT. I still found it hard to believe that this was the complete cause for a boost leak of this caliber. So I decided to put the stock bypass valve back in. This was a good thing because I could also check out the throttlebody and make sure it was secure and not leaking. After making sure all was tight to include the s/c horn, I put the intercooler back on with the stock bellows. Now, except for the clutch not grabbing like it used to in first, this car runs like a dream. I really don't know what caused the car to run erratic, but after putting some of the OEM parts back on, it made a huge difference. It's funny, I was skeptical on putting the stock bypass valve back on as you can tell how much stronger the Detroit Tuned spring is, but I was willing to try everything. The pull is incredible. The car runs sooo much stronger now.

 

Thanks for the writeup. I have read a couple of people don't like the DT BPV and put the stock one back on. I may still take the one off my old '02 MCS, adjust the stop screw to make sure the plate shuts all the way, then swap it out. I'm still undecided about reversing the VGS mod. I love that instant-on boost feeling when I nail it.

 

Well, what's funny is that my OEM bypass valve closes all the way. The only difference I can really tell between the OEM and Detroit Tuned is the spring tension. The DT's spring really is stiff. I don't want tonsay it was the culprit because I changed a lot of aftermarket parts back to OEM, and I think I forgot to mention one in the original post. I also changed the Samco intake to throttlebody tube back to the OEM one. So you like the VGS mod? I've been thinking of doing it. Any feedback would be greatly appreciated.

This update goes back to my original problem where I was kicking codes and going into limp mode. I fixed that and for a while I was fine, until recently. The symptoms started coming back.

 

Yes, I do like it overall. The downside is sometimes I actually get a small yo-yo effect at low RPMs, primarily when letting out the clutch in 1st gear. Sometimes, when I do a mild acceleration in 5th or 6th gear around 40-45 MPH, the valve has a tendency to just open and close. I recall somewhere in the VGS mod thread a suggestion to stuff a small amount of cotton into the tube tip on the bypass valve. This helps smooth out the transition.

But that instant-on feeling I get when I do a moderate or hard acceleration... I can't pass it up! It's especially cool when you accelerate hard in between the twisties. Good ones where you are doing 3,500-4,000 RPM between 3rd and 4th gear.

I'm not sure if my valve shuts all the way. I have not taken it off and performed an inspection. I do know I've seen boost levels as high as 16.3 PSI at top end (converted from a metric measurement of 1.125 BAR on my GReddy boost gauge). 1 BAR is approximately 14.5 PSI.