Hi Larry. Hope this helps...
The following info is derived from my genuine Bosch Fuel Injection catalog, North American version, dated 1993. Guess it is not absolute gospel....but surely right from Bosch should be as accurate as you could get....
The fuel injector for all X1/9 1980 to 1988 is listed as Bosch # 0 280 150 123 and is Fiat # 4430293. It is only also common to Fiat Strada.
The fuel injector for 124 spider and 131 1980-1981 is Bosch # 0 280 150 121 and is Fiat # 4393596. Common to nothing else.
The fuel injector for 124 Spyder 1982 is Bosch # 0 280 150 127. No Fiat # given. Common to nothing else.
Strangely....the catalog does not list the 124 spyder at all past 1982 ( and neither under Pininfarina ). Nor do they list any Lancia models at all. Using those Bosch #s in a google search indicates they also fit some later euro models like Argentia and Dedra and such.
So....are the X1/9 and 124 injectors the same ?? Tough to tell !!!!! And depends who you believe LOL......
MWB - and some other aftermarket efi suppliers claim that all the above injectors are all the same. With MWB claiming the only reason for different Fiat and Bosch #s is that.....the injectors are supplied complete with the inlet hose already on them, and that the hoses are different length between the X1/9/Strada, and 124/131 applications. Hence the different parts #s - but they say the injectors themselves are the same - thus identical flow, etc.
On the other hand....other web sources that give flow specs for different Bosch injectors, actually show slightly different flow rates between the 121 and 123 injectors.
Verdict..i dunno for sure where the truth lies. Personally....they are probably pretty close to the same....but dont think i would mix the 2 within the same engine....
As for the cold start valve.......same catalog shows:
The cold start valve for X1/9 1980 to 1988 is Bosch # 0 280 170 031 and is Fiat # 4429210. Common to Alfa Spyder '82-'89, BMW 325e '85-'88, BMW 528e '82-'87, Strada '80-'81, Porsche 912e '76, Renault:Fuego 1.6 '82-'82, R17TL '75-'77, R18i '80-'83, Triumph TR7 2.0 '80-'81, VW: Beetle '75-'79 and Type 2 bus '78.
The cold start valve for Fiat 124 spider and 131 '80-'82 is Bosch # 0 280 170 041 and is Fiat # 4398118. Common to nothing else.
According to MWB......these 2 cold start injectors have the same flow rate and function....BUT...the fuel inlet barb is in a different position. And can be interchanged if you re-route the fuel line to the inlet and use an appropriate longer/or shorter fuel hose.
So Larry...if you have a 4398118....compare it to the cold start valve currently on your X1/9 and see if you agree ??
Hope this helps...but I probably just confused you more !!!!
Doug