From Calibra Wiki - Vauxhall, Opel and Holden Information and Technical Resource
The X25XE is a General Motors engine. It is a 2498cc (2.5L) 24 valve, DOHC V6 engine producing 125kw (170PS).
The break down of the engine name <ref>Topbuzz, "Engine Codes Explained", Topbuzz Website, 2002. Accessed 9 Dec 2006 </ref> is as follows:
X - Exhaust Emissions Level: 94/12/EC, stage 2
25 - 2.5L
X - Compression Ratio - 10.0-11.5:1
E - Mixture System - Injection