they start to balloon or de-laminate internally with age...but collapsing suggests a blockage on the air intake..... possibly your air filter. You see the hoses collapse when you have a snorkel fitted and block the intake... it causes is partial vacuum so that hoses collapse (sucks all the oil out of a k&N filter too
) .... so if your filter is filthy you will get same effect higher up the rev range, or maybe there's just crap in the system, blocked p intercooler etc.... or hoses are in fact de-laminated with age, or you left a rag in a hoses that yo blocked up while changing engine (been there done that)
