prelude motor help (h22aX)

I own a european honda prelude (1999) VTi 4WS.

it has a h22a5 engine in it which is rated at 185hp. the h22a4 (US) is rated at 195 or 200 (5speed)... and in 2000 europe changed to the h22a8, which is 200 hp also.

Does anyone know what the mechanical differences are between the h22a5 and the a4 or a8? This is really important since I need to find out what is restricting my horsepower, or what change of pieces will give me the most gains.

Also, if you don't know, but you know who might be able to answer, please clue me in (honda hq europe, if such a thing exists?).

thanks :D

I found this page:
http://www.acc.eurobell.co.uk/mycar.htm
Where (as well as details of his previous Citroen ZX Volcane) he gives the differences between the A5 and A8 ("after much research") as:
# Air intake ducting/filter housing,
# Camshafts with increased lift,
# Catalytic converter is a larger size,
# Different pistons giving a higher compression ratio,
# Enlarged throttle body from 60 to 62 mm,
# Exhaust manifold / down pipe,
# Exhaust piping has an increased bore of 57 mm instead 51 mm,
# Flexible pipe before the catalytic converter is shorter,
# Optimised ignition and injection timing,
# Valve seats readjusted from 60 to 45 degrees,
# Last but not least, the valve cover is red.