Tell that to all the guys making anywhere from 600-900whp on stock internal n54s. There are plenty online just a quick google will do. The n54 is the new 2jz and we are only at the beginning of it's development cycle; I'm sure there will be built and stroked n54s pushing past 1000whp in the near future and even further than that after a while. One of the best motors BMW has made in a very long time.
and yes single turboing an n54 to the high 600 low 700 horsepower range would cost about that. You don't need to rip the engine apart or anything, just basic bolt on turbo kit, exhaust, upgraded intercooler, clutch kit, higher flowing fuel pump and injectors and an e85 tune. DIY and you would definitely do it for 10-12k budget. You could go further though, and add a better radiator, bigger fans, oil cooler and tranny cooler. Highly advisable if you live somewhere hot and are going to daily the car.
It does have reliability problems, I've known dozens of owners and a handful of lemons
The engine itself can hold power, not debating that, but u are suggesting a 15k used bimmer which is going to be high mileage, and then throw into mods on a car with high mileage, reliability issues, good luck daily driving that...
Of course there are guys with 700-900 hp, it can be done but still it isn't as reliable a rb26 or a 2jz
Cheap and German don't go together
Like I said save yourself the trouble and build a civic with a k20/24 swap or an American car which will be cheaper if power and straight line is all u care
Up to me I'll build a gtr since it's awd/dct tran, them and the turbo lambos have been dominating for years
Maybe also a corvette or viper
Btw I've owned a new 335 back in 09, good car, but couldn't get rid of the 996 turbo at the time
