Check for oil leaks from the 2.0-litre’s cam covers and the sump cover. Cast hypereutectic pistons on the 2.5 (2.0 has forged items) suffer damaged ringlands. The head gasket on the 2.5 is also prone to failure. Engines tuned for 350bhp or more should have toughened internals. Check the claimed power output and fuelling on a rolling road. Ensure the seller allows the oil-cooled turbo to idle. Inspect the condition of the intercooler fins.
OIL AND SERVICING
Check for regular oil changes and that 10W-40 or 10W-50 fully synthetic oil has been used. Service intervals are every 10,000 miles. The engine runs best on Shell V-power or similar grade.
Inspect the rear diff for leaks and listen to whines and clunks from it, the rear diff and the centre viscous coupling.
SUSPENSION, BRAKES AND WHEELS
Rear struts can suffer stiction as the damper rod seal dries out and loses lubrication.
Rear wheel arches are starting to show a little rot on some cars (hawk-eye so far not affected). Front radiator support panels rot, as do front C-subframes (not fitted on imports). Look for rust behind the plastic undertrays on hawk-eye models. Uneven shut lines may indicate crash repair. Check aftermarket headlights for proper alignment and mounting. Tell a 2005-reg blob-eye, wide-track STI from a ‘standard’ 2004 STI by the plastic trim that runs around the wheelarch into the rear bumper.