That is absurdly not true. Any motor will detonate quickly if not built correctly. But, as Jay and Mike said…
LS/B20 non VTEC head flow very poorly, and require HUGE amounts of very careful portwork to do much of anything. N/A, forget it… but it boost you can deal with one, even without porting. VTEC heads flow very well, even in stock trim.
Find yourself a VTEC head, convert and see how you like it. They’ll last just as if it was a factory VTEC motor, provided BOTH the tune and build are done well.
The head and all things needed to convert, can be had cheaply and locally. Be patient and look around. If you have little cash to toy with, then I would not go any further into “building” than that.