[Dave92N54]

Replace any and everything you can with it out. Do rod bearings, every single gasket (valve cover, oil pan, oil filter housing, the vacuum pump seal on the front. Front and rear mains too). Get a front crank seal protector. If the injectors are index 12s, redo the seals and decouplers, if not up to you if you wanna try and ride em out for a bit but at the very least change the seals and decouplers. If it were me i'd do the water pump and thermostat as well. Check all your pulleys, if any are bad i'd just replace them all.

This is your perfect opportunity to address every common issue the N54 has with the most ease you could ever have and have an absolute blast with it. You say you got it for 1k? You have the perfect opportunity for a very fun and decently reliable 400+whp car for an incredible price. If you wanna spend the extra for some upgraded turbos (or turbo if you wanna do single), a solid 500whp with some decent overhead is totally within reach as well.