06 mustang GT MODS:
Saleen SC 3.4 pulley
MoSaleen pulley kit 2" shorter belt
BMR billet lca's
steeda adjustable uca
frpp 4.10's
Mcleod RST clutch & Mcleod billet steel flywheel
few other supporting mods.

Anyway in 2nd and 3rd gear at WOT the boost gauge hits just below 9psi and stay no bounce no jiggle car feels great pulls hard nice and smooth, when I shift into 4th under WOT the car shakes like all four wheels are out of balance, the steering wheel shakes back and forth the boost gauge bounces between 6-9 psi it literally feels like it going to shake apart, it has even caused a rattle in my dash now.

Has anyone experienced this problem? I am at a complete lose.

 

ok i'm going to go with a spark plug or an
injector issue.

i have no idea either sactown, but i do hope
the problem gets fixed soon.

 

Putting it on the dyno tomorrow, with new plugs and a compression test, but I don't think that is the problem. This is very weird no body on 3 other forums has any idea either.

 

let's see what happens on the dyno, it
will be interesting.

 

Could it just be related to the speeds you are going in 4th gear?

The wheels, DS, or other components might have a speed related vibration.

 

The car was completely fine on the dyno, had the tune fixed. Dropped the DR's off to have them rebalanced waiting to hear what they come back with. I will post if they find that they were out of balance or not.

 

ok now let's see what happens when you
get her out on the street again and see
how she does, this will be interesting too.

 

subscribed....sounds like what Vapor trails was getting at?.....

 

DR's were out of balance by a couple of ounces, and the tire guys said (which I have noticed) they are shapped a little funny oblonged from doing burnouts. Going to the track tonight to see if I can just finish the tires off, don't think I will be getting M&H's anymore. They hook like crazy but wear out very fast this is my 2nd set this year, my MT ET streets lasted twice as long and never had this weird problem, if in fact its the DR's.

 

Hopefully thats all it is sactown....keep us posted!