1994 3 L pickup
i just put in a K&N cool air intake last night and when we started it up it was running fine. then after driving about 2 blocks it started to misfire and when you depress the clutch or let it idle at all it drops down to a point where it stalls slightly then shoots up to 1500 RPM then drops down to nothing then goes up to 1500 RPM and this goes on and on and either just does not stop or will actually stall.

any help would be great
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Did you make sure to plug the Airflow meter back in? And that your air ports are properly blocked or capped?

 

sounds like a pretty serious vacuum leak to me.
like DeathCougar asked- is the AFM reconnected properly and all tubes and ducts connected or plugged?