Engine looses power/torque, gets a bit jerky and seems like it wanted to stall (stall might be an overstatement though) while accelerating say on 3rd gear between 2000 and 3000rpm (it is non-turbo EJ204 2.0X MY07). Fuel pump? Fuel filter? Dodgy fuel? MAF? ECU related thing? Everything else seems to be in right order- correct idle, correct temp and all that.