burty

help !! i have a my03 imp turbo which has a flat spot/hesitation that is very apparent it 3000 to 4000 rpm after that it just feels a bit lazy.i have tried new maff,plugs,boost sol.,pipe work all over,air filter,fuel filter, changed oil?,injector cleaner, and eaven a good thrashing!! been doing a search .. could it be a coil pack??

any help will be mint, many thanks