There are more than a few possibilities: For one, the fact that it knocks while climbing tells me it could be the EGR valve and/or it's electronic control. I'd take off the EGR and it's exhaust tube and clean the carbon out of them (don't get any cleaner on the diaphram in it or it will eat it up). While you have it off and cleaned try blowing through the egr valve. It shouldn't let any air pass unless vaccum is applied to the little port. You can also try testing it with a vaccum tester (rent one free at an auto store). Put the proper load on the little port and see if it holds that load for a minute or so. I'd also clean the MAF with some EFI safe throttle body cleaner. Next, clean the throttle body. Is it fuel injected? If so, use EFI safe cleaner on that and take a soft scrub brush and brush out the carbon as well. Still have a problem? Next check the IAC as it can have carbon build up on it. An 02 Sensor is also a candidate to replace if it's got more than 30 or 40 thousand miles on it. Put a bottle of injector cleaner in the gas. Beyond that, the throttle position sensor could have some dead spots in it.