I'll give it a go..
hay man, I hasd the same fing hapen wen I had my furst R32 ay?
it had a hektik az blow up valve on it and wen i came off da gas pedal it wood make a maaaad psshhhttt sound ay, but strayt afta dat, da revz wuld go reel low.
i den went an got a stoka blo up valv and mayd it all like a stoka setup ay, and dis fixd the stalling and da low revs.
so yeh, get a stok valv an it shuld fix ur carz problm