Volvo: 1992 volvo 940GL rough start, volvo 940gl, vacuum leaks

Question
I have a 1992 Volvo 940GL that is rough to start and stumbles for about 20 seconds after starting and then it's fine. Had fuel injectors cleaned, replaced fuel and air filters. What's next?

Answer
Larry,
Perhaps one or more cylinders are not firing at first start due to plugs cap rotor wires. Could there be some vacuum leaks at the intake or some vac lines? Is the fuel pressure too low. Could the engine just be so worn out that the compression is low and gives a bit of hard start? Is the gas of very poor quality and not firing well? Too much carbon on the intake valves that the fuel is soaked up by the carbon, causing a lean mixture in that cylinder for a few moments.