Hi, ive got a au2 xr8. Its april 2001. Ive been doing some research about the motor. I pulled the rocker cover off on the weekend and its got gt40p heads and yella terra rolla rockers on it. But its only got the smaller throttle body on the manifold. Just curious if it was only the throttle body that was the difference with motors or the tune also. It did have a twin exhaust system and tickford intake on when I bought it but the exhaust was shagged and replaced with a manta system.
Any help would be appreciated, also would I gain anything by pulling the manifold off and removing the burrs and general roughness of the casting inside the manifold?
Cheers

From numerous posts about these engines, here's a summary:

The 220kw engine had 9.4:1 comp ratio, mildly ported GT40P heads, 1.7 roller rockers, .455/.455 lift cam, double valve springs, 70mm throttle body, extractors and exhaust.

The 200kw engine has 9:1 comp ratio, stock GT40P heads, 1.6 roller rockers, .458/.458 lift cam and a 65mm throttle, extractors & exhaust.

Cleaning up the manifold would improve airflow slightly. To make any significant gains, you need to get the heads ported, or better still replace them with aluminium ones that flow more. Depends on your budget though.

Also I think the later 200kw got the yella terra rockers, I know mine has them. the 220 also has a slightly ported lower intake near the head.

220kW started build June 2001. So yours has to be the 200.

For the record the 220 heads were pretty shameful in their quality. They had the specs but mine were all over the place for spring tensions. Good strong combo though even if the LS1 killed them for same power rating.