[v8volvo]

Congrats and welcome, sounds like a fun plan. These respond well to being turned up a bit, you'll be able to get it performing like you want without too much effort. The fact that you are starting with the IC motor gives you an advantage too.

I'd say you're on the right track with initial steps to get a good baseline setup. Timing belts, water pump, idler rollers/tensioner, set cam and pump timing to proper spec using the special tools. Make sure the bolt on the front of the crankshaft gets its correct torque using the special tools for that. Your late IC motor likely has hydraulic lifters but if not, check/adjust valve lash.

Replace fuel filter and air filter with good quality parts and ensure the airbox thermostat is working or stick it in the cold position, if your car has one. They can fail in the warm position and suck hot air all the time from the preheat hose which cuts down power. When replacing the fuel filter, prefill with clean new fuel or ATF, and make sure there are no old inner O-rings stuck on the filter nipple, sometimes they like to stay there and cause problems later on.

Replace the thermostat; I like to use the 80C version (may need to spec it for an Audi since sometimes does not show for the Volvo application) since it helps keep temps in check on long hills in hot weather, but if you never see high temperatures or do mountain driving the regular 87C tstat is OK. You'll be able to make whatever power you want with the engine, but the performance and integrity of the cooling system will determine whether you are able to reliably use it. Cooling systems are sensitive on these and the motor doesn't tolerate overheating, so give some attention to hoses, fan clutch, radiator, etc. Make sure it stays on proper temp at all times and if anything is marginal, replace before running it hard.

Check the cold start device for proper function; when they fail, they fail in the cold position and run the engine with too much timing advance when hot. As the engine warms up, you should be able to see the advance arm on the side of the pump back off fully to its stop, and if the idle and pump settings are set up correctly, you'll notice the idle speed drop from high idle to normal idle when warm. If it doesn't move, you can replace the wax thermostat that runs the system, or temporarily (or permanently) disable it in the warm position and live with rougher cold starts and no fast idle. Some folks don't mind this or live in warm places where it's less of an issue. I prefer to keep it working properly since it's a benefit in the cold months.

Pulling injectors and having them checked is never a "bad" idea; but you may find they don't need it. Still could be fine at that mileage and nozzles and injector work can be costly. If you're having them out, remember to replace the heatshields and overflow hoses, and it would be a chance to also check compression if you are curious. Replacing at least the two rear glow plugs is always a good idea if the injectors are out too, since they are a pain to reach at any other time. The front four are easy to get to. However, I would probably leave all of this for later and put priority on the other work you named first. You'll probably be able to get it running very well on the injectors that are in it now and look at them in the future if desired. At 140k I would not expect new nozzles to make a noticeable difference.

If you say it's especially slow off the line, that could be due to timing being off from a previous belt change. Decent chance that just doing the basic maintenance work above will give a significant increase in performance. Beyond that, turning up the fuel a bit will give more response, and especially since you have the TIC motor, you should be able to get good results from increasing turbo boost by a few psi in addition. There are diminishing returns on this with the stock turbo so want to avoid going too far but you can get some nice extra push with a mild increase and no sacrifice in reliability or bottom end.

Beyond the initial upkeep, always use good full synthetic oil and keep an eye on the cooling system and it will last you as long as you want, with good performance, excellent reliability, and low ownership cost. Lots of good knowledge on this board if you ever have questions. Enjoy and let us know how it goes!