I have a 2006 2.0 diesel Mazda 5. It was struggling in 2nd gear, got it serviced and engine cleaned and new egr valve. When driving 60 mph plus and overtaking it blows smoke out of exhaust in massive plumes and car struggles. I have had it in garage who checked injectors and fly wheel but mechanic cannot identify the issue. When I park it up it spews out white smoke but as soon as I press clutch the smoke stops. Any help would be greatly appreciated.