My 94 850 turbo is missing and backfiring. Black smoke when revs up. on 1994 Volvo 850

We have checked fuel pressure ,at 40 to 60 pounds. Is this the right range? We have changed fuel filter, spark plugs, checked distributor cap, and timing. Any suggestions as to why it may be stalling out and running rich?

Asked by for the 1994 Volvo 850
Fuel pressure sounds good. Have you checked for any trouble codes? Is the check engine light on?
no engine light coming on...