I tried ETTC on my '97 "Jewel Green Pearl" Auto Car. In TTC mode, the car would hold a set boost level to 20psi.
Maybe your switch setup or VSV's are bad. Sounds like a VSV is closing and not allowing intake air into the 2nd turbo IACV. Or, it could be the EGCV not staying open... Probably a faulty Pressure tank which is used in ETTC to open the VSV's for TTC mode.
So, now you can check it out by watching the EGCV and IACV actuators. When you switch the ETTC, you should see them opening. If they are not opening, sometimes you can actually hear them popping a bit, then your pressure tank may be bad.
Hope this helps...not sure if all the details and acronyms are totally accurate, however the general concept that with ETTC the VSV's are operated by the pressure tank. So, it's either the VSV's or the pressure tank, or your wiring, or other....
Maybe your switch setup or VSV's are bad. Sounds like a VSV is closing and not allowing intake air into the 2nd turbo IACV. Or, it could be the EGCV not staying open... Probably a faulty Pressure tank which is used in ETTC to open the VSV's for TTC mode.
So, now you can check it out by watching the EGCV and IACV actuators. When you switch the ETTC, you should see them opening. If they are not opening, sometimes you can actually hear them popping a bit, then your pressure tank may be bad.
Hope this helps...not sure if all the details and acronyms are totally accurate, however the general concept that with ETTC the VSV's are operated by the pressure tank. So, it's either the VSV's or the pressure tank, or your wiring, or other....