backing off in 4th and 5th?

[newbstar*]

havn't had a chance to have a look yet.Car at 3000-4000rpm in 4th and 5th gear all of a sudden holds back like lack a of spark.Good power all through the rev range in all other gears.Also is not misfiring that i can tell, If you let the power build smoothly its ok but if you try excellerating hard it holds back big time in the gears mentioned above.
Running only 12psi at the mo carb top 5 gt turbo.
Wonder if its coil ? Thoughts please peeps:(

[Dave Reed]

Sounds to me like a fuel issue.
Check that the boost hose going to the FPR isn't split and if it isn't that then you need to check the fuel pressure.