Please can someone tell me the difference between Honda i-Vtech models of car to normal models?

Honda V-tech engines have an extended rev range, courtesy of variable valve timing, as well as a special intake plenum. Intake plenum has 2 tracts, a short one for high rpm, and a longer one for low rpm, to boost torque.

The intake plenum and valve gear are controlled by signals from the engine, via the ECU, and a changeover solenoid that determines which tract (long or short ) will give the best response for a given engine rpm / load.

Check http://en.wikipedia.org/wiki/VTEC for a definition of what vtech is. Peace