Your problem sounds just like mine.
I'm on my third set now after 284,000 miles and 24 years of owning my 1988 Mk1 Golf Gti cabriolet.
There is 2 types of injectors, later type - air shroud type which have a cap on then end of the injector and an air hose going the the head between cylinders 3 and 4, or early type - non shrouded type with no cap on the end of the injector.
later type are now getting harder to get so the price has gone up.
Pull them out and test them, pull out the fuel pump relay and the relay below it, take the reply from below and get it to fit in the fuel pump relay socket in the fuse box, the fuel pump should run as soon as the ignition is turned on, lift the air flap in the metering head and fuel should spray out of the injectors, spray them into some jars then clean with a cloth and wait to see if any petrol drips out on to a bit of kitchen towel, it may take a few minutes.