Im not saying its 100% safe, but having comp test is better than nothing. We all know that one of the common reason to sell ur car is there is sth wrong with it. From my experience, 08+ sti failed I know of is cause by owner with little mechnical sympathy. 11+ stis can also have ring land failure, i think they have slightly stronger head studs and piston rings than 08 sti.

If op can afford 11+ that's perfect. But a low km 08 sti with good comp test result is not a bad option.

Im no expert, just wanna give some help too

using the Perth-WRX mobile app

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport