Low boost stutter

I have had a problem for a long time with the car bucking at low boost part throttle, such as passing someone while in 4th or 5th gear. Exactly like this post that no one ever solved:

http://forum.turboford.org/cgi-bin/ultim...010#000005

I got used to just putting the pedal down further so I wouldn't have that problem. Now, I have to drive on the highway at about 75mph for 20 minutes every day to go to my new job. At 75 it does the same thing as when I try to pass at part throttle. It bucks and sputters, I tried to just put the pedal down some more after it started and it just backfired and bucked harder so I have to let completely off and reapply the throttle. If I slow down to 70, I won't have the problem.

It has new plugs, wires, coil, BP Sensor, TPS, complete distributor. I'm at a complete loss.

Backfire can often be a sign of a timing problem. I'd start with checking the cam timing and then the ignition timing.
I'd also look for a air leak ahead of the throttle body.

I triple checked all of the hose connections, the cam timing is good and I have ignition timing at 12*. I just checked the vam and my VREF is 5.98V and when I open the door inside, the signal goes from .28V to 5.5V. The write up I used to test it said that the signal should be 4.5 Max. I tested 2 different Vams and they both had the same reading.

Mine was doing this for awhile just prior to the timing belt going out. A couple bad/missing timing belt teeth were causing the issue, then the belt lost a bunch of teeth.

It has a new timing belt and it did it before the belt change.

What about hose leaks. VAM hose can wear on the bottom side (out of sight) and I've seen IC hoses split and crack (BTDT)

Vam hose checks out I took all the silicone couplers loose and inspected them and they check out too. Any other ideas?

What Pete said. Sounds like cam timing maybe a tooth off. Although, mine was a tooth off when I changed the timing belt over the weekend and it ran like crap. Sounded weird when it idled. Kinda freaked me out so I redid the cam timing. Purred like a kitten.

If you can get ahold of a scanner, check for codes. Might be a problem that only shows up under certain engine parameters.

On a side note, my car did pretty much the same as yours on a couple of occasions but that was before I put the new timing belt on. Only driven it once to work. Once my clutch is broke-in I'm gonna romp in it to see how it runs under boost.

Good luck.

if you run and egr, try disconnecting it and/or blocking it off & see if trouble persists.

if you have the BOV vented to atmosphere, try increasing the spring preload.

if these dont change the behavior, i'd wonder if maybe a slight increase in fuel pressure might help. isnt it possible that the bigger turbo, engine rpm, and cam timing hit a "sweet spot" where the afr is outta wack... do you have a wideband o2 or can you log afr's at all?

Did you check fuel pressure?