Hi folks, My S4 has a slight hesitation when charging throughthe gears at around 3200 rpm, more noticeable in 3rd and 4th gears. It pulls like a train until 3200 and then it's as if someone is lightly pressing the brake pedal, the after 3250 rpm, it's pulling strong again. My S4 has an APR stage 1 and has always had a slight hesitation at this engine speed, but it is getting noticeably worse. Initial thoughts are a leaking diaphragm on one or both dump valves (standard), but I haven't checked yet. Thought I'd run it past the forum to see if anyone else has had similar symptoms? Any advice, most appreciated. Gaz.