After 4.5K RPM my boost drops from 11 to 5 and never builds back up. Sometimes at WOT I can only get 5 psi. I took it to a shop and they replaced a few check valves and hoses, but were still unable to fix the prob completely. They suggested that a downpipe might be the answer. Thanks for the help in advance.

 

Search this forum. There are so many people with boost problems. There are many answers to your questions grasshopper.

 

Depending on what mods you already have on the car, I would put a downpipe on it anyways. The 5 pounds of boost after transition is typical of a clogged pre-cat but it could still be something else. Whether it fixes the problem or not, you're better off with a precat (unless you already have a cat-back and intake on it).

 

A clogged cat(pre or main) will also reduce boost before 4500 rpm. You have a control problem with
either the charge control solenoid or charge relief valve most likely. Could be caused by bad
valves for the pressure or vacuum tanks also.

 

I think I have the same problem. I think my precat is clogged since it glows orange , and my boost patterns are as follows:
10-5-10 but right away it drops down to 5 psi. Seems like it doesn't hold its boost. Opinions?

 

When my precat was clogged, it made good boost on the primary but just never recovered after transition. Is your precat glowing orange after its been sitting there at idle for several minutes, or right after its gone for a drive? My downpipe will start to glow if I just idle the car for extended periods but it will "cool off", if you will, after its taken for a drive. If you're making good boost after the transition and then losing it, it sounds like you're bleeding it off. You might have the problems Chuck was describing.

 

My precat glows after I go for a drive. Someone said it could be running really rich. I know one of my injectors has a slight leak to it. I don't know whether this contributes to it running rich.