I agree with Trinker's thoughts: a failing turbo shouldn't cause white smoke or misfiring. White smoke is from poorly-combusted fuel, caused by being injected at the wrong time- and you *have* just worked on the injection pump...
I'm going to presume it's not the turbo. It's odd that it only shows up when it's warm. Does your injection pump have a cold-start doohickey? It'll be on the end of the advance plunger like so:
- dsc05348.jpg (562.86 KiB) Viewed 6342 times
...though the appearance might be different. If you don't have one, that position just has a metal plate with two screws, and an o-ring behind.
I ask because that's the only thing I can think of that deliberately changes with temperature. If you have one, then maybe it's not assembled correctly.
Other things that can cause misfiring at higher speeds (but not necessarily when hot):
-Air in the injector lines (compresses and alters the timing). Give them a good bleed.
-Restriction in the tiny fuel screen in the pumps' fuel inlet banjo (if fitted. Changes the pump's internal pressure, which controls injection timing))
-Sticky advance plunger (mine was sticky from someone assembling the pump with silicone sealant. Ugh. All seals should go in dry.)
-Air leak from a damaged/improperly installed seal (usually causes hard starting though)
-Sticky/dirty injector- The little needle on the end is very delicate and will cause no end of troubles if the injector is dropped. They also don't like dirt in their fuel, was there any chance crud got into the fuel inlet?
Apart from those things I'd check all the things that were moved during the recent work. I'd be looking for fuel leaks, but also checking that everything is tight: A loose injector or delivery valve might be sealing fine when cold, but allowing air in when hot. A single head bolt that's not torqued could let air in. etc.
Nothing says "poor workmanship" more than wrinkles in the duct tape.
