What is the 4 cyl /9/1 engine valued at? Whatever that value is, X 1.23 would be the best real value.

If the GTI is 90, the 5cyl is 110.
The 5cyl shares most specs with the 1.7 engine,
/ 5cyl had the small valves, shitty cam . These items reduce the power range to less than 5800 .
If the cars are run much over 5800 the engine specs are most likely OOR. IMHO.