I voted nothing. Building up the suspension, brakes, throwing a cage in it, and hitting up the road courses. If you like adrenaline its the way to go
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If you really need boost though I'd probably suggest just keeping the DET. You don't need a gti-R or a VE/DET for 300whp.
Since your in ontario you can hit up Tiger Japanese and just pick the motor that seems the best to you.