ive got the expensive one the Pro RR one, its dead accurate, proved at santa pod last weekend on 1/4 mile, it was 2 split seconds out on santa pods timing system,

The bhp bit is good, ive tested on standard cars 2.5V6 omega, Gtech said 172bhp,

My Punto GT, Gtech said 133Bhp

Mates MR2 Turbo, Gtech said, 232Bhp

All standard cars

Not bad really

30 quid are suspose to be crap though, mine was 200