hello members can you help me please

i have a 2007 1.8 tdci ford c max i am getting poor fuel economy i am getting around town about 37.2 on the motorway it much the same whats could can cause this problem i also noticed you have to excelerate more when pulling off the car drives ok but sometimes feels to lose power i have changed the air filter the other day this was all clogged up what else can i try

hope you can help