I replaced the cigar hose on my 85 CA 300D soon after I bought it, thinking that hose was abnormally swollen. The rubber was a bit old anyway. After many years, I read that the larger size was intentional so replaced it with a new, correct cigar hose ($9 I recall). The engine failed at 330K miles, but probably unrelated. I don't recall the exact chronology and may have changed it after the failed engine. I don't recall any change in idle or such.