I bought my manual 06 wrx back in June with 135k miles on the body & 50 something on the engine. The previous owner had a list of things done to it including a clutch & this past month my car started to spike in rpm if I get on the gas. At first it wasn’t bad but now it can be any gear any rpm & if I floor it it’ll slip. My dad is a mechanic & has been for 20 something years he told me it isn’t the clutch after I asked him but everywhere I look says it is. I’ve put 10,000 miles on the car so the clutch shouldn’t be bad this soon right? Is there anything else besides the clutch that could cause this?? Only mods are a stage 1 tune from Cobb on 93 octane, cold air intake, Sti intercooler, air oil separator & a turboback exhaust. Any help would be appreciated I’m fairly new to the whole car guy thing.