300bhp is just a number for pub bragging
Drivability and power throughout the rev range is what you want.
Cheapest way to 300bhp is a k04 turbo, DV relocation & discharge pipe, exhaust downpipe / decat (or sports cat) panel filter and a proper custom map. The standard injectors can flow 300bhp so that's all you need. . .
That should just nudge 300bhp, failing that, a K&N typhoon (cheapest induction kit) will do it
(out of the box maps such as revo or superchips will require upgraded injectors)
Graeme