Nothing at all wrong with the C1J, in many ways it's a more reliable, if not bulletproof design, given that it's tuned correctly, with correct fueling and a adequate cooling system for the oil and water.
The problem with it there are a bunch of complete amateurs out there (some tuners included) who have no idea how to tune a car (generally the turn the boost up and chuck a bigger jet in the carb variety... oh and the same people usually take the out the thermostat out of the engine as well.....
)
There are lots of members on here who have reliably run 200+ hp from the C1J. Put together by somebody who knows what they are doing with the right parts (you don't necessarily need forged this and uprated that) they are a very simple and reliable little lump and if you're planning on using one as a track toy, you don't want to be putting more weight in the front.... theres a lot of info on here about that kind of thing, worth a dig about...
Also above 220hp there's little use for any extra power, you want to be thinking about how to get it down.... ie ltd slip diffs, suspension, tyres etc