Rob is right , do the easy things first all gas filters--gas flow test --I had a similar problem --Turned out my tach was off hundreds of rpms, and I was over shooting my shift pts---If every thing checks out------ get on a dyno and do a complete basic tune--checking as you go--At least you will eliminate the things that are working----If that nose -down feeling is happening right from the start--Rob could be right about the valve floating---------But make a simple check list and follow it thru---I'm sure you're doing this anyway---Just a Gremlin (
)--- somewhere------------------