Vauxhall Meriva sluggish

Simply put, when the accelerator pedal is depressed, there is a delay before the engine revs kick in. The result being that when driving there is a very slow response to speed increase through the gears. EML remains off, so not indicating any faults. I have replaced the throttle potentiometer, cleaned the throttle body and EGR valve with Carb cleaner. Also cleaned the MAF sensor with electrical contact cleaner. All to no avail. Any suggestions as to curing this problem would be both welcomed and very much appreciated. Thank you in advance.