hey Paul the primary on my Legacy kicks in at around 2500rpm but also depends on whether car is on load up hills etc...I would watch out for previous owners playing with hose 10 & 23 on primary causing it to have higher boost and wear out faster, knock sensors failing and having to be replaced (they are a bitch to get to and a relocation might be necessary), air getting into the cooling system when you refill (see technique on here for ridding all air pockets), dickhead drunk people who like to rip your monsoon shields off and smash windows in the middle of the night and Big End Bearing issues if your not regularly servicing the vehicle and using good oil...