UKC

Not eating meat often, I occasionally hanker after this or that.  At the moment it's chicken chow mein; specifically the version that was done at the now-closed place where I used to live...which isn't much help I know.

Do you have an authentic (in the english takeaway sense rather than the at-home-in-Xi An sense) recipe?  I never seem to get it quite the same.  I don't do MSG, so maybe that's it.

Have you tried with cat rather than chicken?

See my definition of authentic

More seriously make sure you are velveting the meat .

Do you have a wok burner and a decent extractor hood so you can keep the wok at a smoking hot temperature? If not the missing flavour may be "wok hei" rather than msg. 

Yes, got a good burner and a well proved wok

The first cow meins I remember were the Vesta ones - especially the fried noodles.

Anthony Bourdain claimed that restaurant food tasted so good because there would be a tonne of butter in your meal. 

Is that what you are missing?
 

First catch your chow....

Right. A wok in the park aka "Wok you looking at"

Or msg?

To the op, try this YouTube channel I think they may have a recipe 

https://youtube.com/c/ZiangsFoodWorkshop

Put the Beansprout's in last don't overcook,Use light soy sauce and a splash of sesame oil to finish.

A large wok and wok stand for best results.

You won't find much butter in Chinese cuisine.

It's probably the MSG...the old wives tale about it being bad for you has been debunked for a long time. 

See the OP's definition of authentic.

Here is a recipe from the China chapter of my water-damaged copy of Charmaine Solomon's Asian Cookbook