I have a 95 12valve 4speed when the truck is in o/d it will not exceed 2k rpm the boost drops to zero for a second and build back 20psi + will continue this yet in every other gear will get to 2300k rpm and no boost cycling . I have had this problem since I bought it 2 years ago I have replaced fuel shut off solenoid over flow valve many new fuel filters cleaned the screen below the filter and installed psi gauge removed fuel plate and have the star wheel 3/4 forward in an attempt to see a difference no luck so far any ideas? was thinking fuel pump timing ?

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forgot to add I clamped off waste gate vacuum tube and no difference except it will build 30+psi
just drove 1900miles and have another 1900 in a week would be awesome to go over 63mph

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also no exhaust just down pipe out side

 

white smoke at all when its cold while reving it? boost line hooked up to the afc?

 

o yea lots of white smoke when cold 50 or below little better with new overflow . gauge is to intake below heater there is a plug I used that port" that 1/8 copper line in pic"

 

just figured I would add 3.5 gear ratio

 

injectors or timing if shes bellowing the white smoke.

 

thx for the replies but I wound up bringing it to a shop there was a bunch of crap stuck in tank sending unit screen and lines when he gauged it the fuel pressure went 0 when on the throttle at all you would think I would have gotten great fuel economy with 0psi but just figured Id post conclusion if any one has a similar problem