Smaller turbo now have flat spot?

[muz]

I've had a 62/71/14 turbo with 5x14 injectors with 10 thou pintle lift on my truck for a long while but its always been a little smokey with a little lag. I've changed the turbo for a 62/65/12 and now it pulls well hits a flat spot (almost like a rev limiter) then powers on again do you think this is a drive pressure issue?

 

[jasonc]

Do you hear any surge when this happens?

 

[muz]

no real surge it just goes flat for what seems like a few seconds then it powers on again

 

[CorneliusRox]

Seems like an AFC or Gov Spring issue to me.

Is it purely RPM based, or purely boost pressure based?

 

[jasonc]

Check or tighten your gate.