how can i fix my v reg zafira 1.8 16v comfort?

thanks for feed back last question was a bit brief because dont know much about cars will try again.
My zafira starts fine, no problem with tickover, engine managment light does not stay on, engine managment was checked in garage nothing came up on computer. If i accelerate gently there is no spluttering, if i put my foot down quicker like to overtake or go up hill it splutters like mad, i changed spark plugs, petrol filter, put forte injector cleaner through system, No change. This has only started happening since it almost ran out of fuel, unable to check EGR valve due to rusted bolts.
any advice anyone can give a dummy like me would be greatly recived, My knoledge is very limited so plain english please lol Also does anyone know where i can can get diorgrams for my car online. many thanks