Volvo Repair: acceleration problem, lean condition, air mass

Question
1992 940 4 cyl no turbo.  There is no acceleration unless you put your hand over the intake, it revs right up. It spits up into the intake manifold like a lean condition.   Sensors, switches, computer have all checked out OK.   Have you ever seen this?  What  could be the problem?  thanks for your consideration.  I haven't been able to figure this one out.

Answer
Hello Dave,  By putting your hand over the intake,you are restricting air flow,limitting the amt to what is needed to run.Now,what part of thr intake are you covering, front of the air mass meter,or mouth of the throttle body.If air is not flowing passed the AAMeter,the engine will not run correctly.What brought you to needing to block off the intake? Curious.PKD