Before you do ANYTHING, take it to Martin Hadland and have the map checked over. Recently he has managed to get 30-40bhp AT THE WHEELS by optimising the "off the shelf maps"!

Once you have done that, you can then try the car in it's new format and see if you still find it wanting .

You may find that the injectors are running out of duty cycle, but a switch to greys would give 320bhp at the wheels with the spec you have .