A sequential blow off valve will not open at any BOOST pressure , it will only open when lifting off the throttle , sequential is the HKS design of valve , there r 2 valves which r sequential in operation.
Sequential blow off valves and dump valves perform the same function but the HKS sequential is a more elaborate and efficient design.
Your car has a recirculating dump valve anyway , but an aftermarket valve will b more robust and won't leak boost pressure especially when boost is raised.
Dump valves which blow to the atmosphere will probably invalidate warranty due 2 controversy that they can damage engines , which in the case of the HKS sequential is rubbish , mine has been installed for about 10k miles with no problems.
Hi Dude, I installed the well lane turbo twin piston dump valve - paid £50 for it which I fink was a bargain! - If its sound you're after then this is amazing.
As far as the warrenty Colt cars state that all you can do to the Evo is an exhaust and air filter - specific - no mention for a dump valve. However - the one I've fitted replaces the old one - no drilling etc - just undo 2 of them clip things add the new one and away you go. I keep my old one in the car so if I do ge a problem - its a 2 minute jobie to change it!!!
P.S. I noticed at Trax that many many many - one for luck many!! people had a dump valve the same as the one I've got - It just said their company name on it instead of Well Lane............