i have a similiar kinda prob with my 97 lancer auto...
try one thing is the problem also there when u driving from a hualt or while in a moving car when u try to speed it up...
there can be many reasons for it proper air flow is one... fan belt alignment etc... in my case venturi is also lil messed up by cng installer...
try to get ur car tuned on cng first and then look for any other issues...
about the shifting it depends on how hard u push ur accelerator... more hard u push more late the shift will be (at higher RPM)