After running pretty low on fuel I have noticed that my marea is running very poorly

Cold start is totally fine and the car will drive normally, until its warmed up then it really doesnt pull well under load, unless I am super light with throttle application, which doesnt enable me to keep up with traffic flow !

The cars revs cleanly and smoothly with no load

Once 3000rpm has passed with a heavy throttle (under load) its fine

Tickover once warm is total fine

Any suggestions ?

No warning lights on dash are on

Carb clean the ICV/Throttle body and MAF, she should run a treat, if not theres a chance one of the injectors is on its way out perhaps, you'd want one of those electric meters which i forget their proper name *Doh*.