I have a wierd turbo bark only when towing my trailer (approx 10000lbs). I can be pulling a hill, approx 35 psi - 40 psi boost, 4th gear locked up, slight flutter in the boost guage, then a sudden bark ( 0psi on guage), then recovered immediately, good for another 15-20 seconds, then did it again. Not the best noise to hear, freaked the wife right out!!!!! Any ideas??? TIA