Re: 145 v 146 v 155 v 156 2.0 ts engines
the later 145/146 engines (155bhp as opposed to the earlier 150bhp engines) have variable length inlet manifold. A plastic chambers of flaps and motors... doesn't fully open until about 5k rpm, then (with a cone air filter) suddenly drops in tone and gets louder. Was introduced for noise emmissions. They explode/implode quite spectacularly apparantly when they go wrong!!
Also the later 155bhp 145/6 variant has the placcy cam cover cover(!) and the same ECU as the 156/147 - mounted on top of the throttle body as opposed to under the carpet. The ECU on the throttle body is not swappable EEPROM - only serial reprogrammable as opposed to the earlier EEPROM type. Both still Bosch
I believe all engine internals are the same (apart from updates of course) with the only difference being the (minor & swappable) ancilliaries.
Websites are like ********s, everyone has one, and im wary of any bloke trying to direct people into their's