iv heard you can fit a gtech chip to the 20vt but what are the boost controller kits can you up your boost at all to a safe limit without changing the intercooler or is it advised not to
Okay the boost controller kits are just that, they control boost. Specifically - they can hold boost higher up the rev range using the same turbocharger than the standard EBV or an aftermarker PRV, PBV or whatever. They range from £100-£500, and typically comprise a solenoid unit, control unit, and display.
You can increase the boost without uprating the intercooler, but I'd go no higher than 1.1 bar boost personally in the hotter months, just in case. In winter, 1.2 bar is okay too