1990 volvo 760 will not get above 3000 rpm

[angeltease]

My volvo will not get above 3000 rpm. My husband thinks the turbo is clogged and is about to replace it. We started having issues when he had to change the throttle cable because the old one was frayed and broken. When it gets to 3000, it drops. I do not think anything is wrong with the turbo, and i dont want him to replace it for nothing.