I've done over 10k miles with my 1.8 8v. As with an earlier cross flow, I've never noticed any problem with the 40s. The 1.8 8v has been on a rolling road to try and sort out a timing issue. At the same time carbs were checked and jets adjusted but not, as far as I can recall, radically. I suggest its a case see how it goes and if OK leave alone.