Hi and hope help is near...

I have a caddy with a vr6 conversation AAA code( don't know much else) 

It has a real lack of low down throttle response and runs very lumpy until it hits 2.5/3 rpm then takes off like a vr6 should..

I have replaced ht leads and plugs to start looking for a few other maybe's...... Coil? Maf? Coolant sensor?

Hi....welcome to the Forum

The fact that it is 'on song' at higher revs suggests that it is something like a vacuum/air leak in the in the inlet manifold or associated trunking which is causing the lumpy running.

A quick emissions test (Oxygen levels) which if higher than zero suggests thats the fault.

Let us know how you get on with it

Cheers,   Trevor