1996 subaru twin turbo runs perfectly fine but when warms up check engine light comes on and stays on without flashing

check the turbo actuators are working . Check vacuum hoses for cracks. Check sensors that activate the actuators

a common part over looked when a turbo is bad the drain tube gets plugged and oil cant drain

The check engine light is indicating there IS a problem and yes, your cars performance is being effected. And since the car is older than 1996, a diqgnostic computer is out of the question.

Most local parts stores like Autozone or Advance auto will check the trouble codes for free and help you get the parts you need to fix whatever is causing the engine light to come on.

sending unit may be faulty replace with new unit also check for a loose ground and or alternator belt

Hi, have the same problem with my 1995 legacy gt twin turbo and the problem lyes with the ecu temp switch, it sound's like the ecu thinks the engine needs more fuel to start and run

I don't know much about Subaru but I expect the turbo wastegate is controlled by vacuum which is switched by the engine management system.

In the old days the turbo wastegate was normally closed and the manifold pressure was fed into a servo which opened the gate at the predetermined pressure.

The new way of doing things is to have the wastegate normally open and the turbo producing no pressure until the engine management decides the time is right and it switches a vacuum supply to a vacuum servo which then closes the wastegate. With this system the wastegate is constantly moving and so is unlikely to give trouble though the vacuum servo sometimes leaks and vacuum lines give trouble.

A fellow I know had a similar problem where the engine check light would light up and he would lose performance. In theory this was because of an overboost condition but the repair shop after fiddling around with it for a week fitted a new EGR valve to produce a cure.

well i would check the cat. and the turbo wast gate, check iner cooler for clogged system if this dose not help you let me know and i will give you more info is there check eng light on let me know

hi i had that fault i found it was a small box the size of a fifty pence on the osf with a small air pipe coming from the bottom of it try a run the car then take the pipe of if its working you will see the change in the engine

it is possible but regardless they need to fix.
get that in writing in case something happens to engine they cant say you drove around with light on so no warranty