Then yours isn't working properly. I have the E36 316i 1.9L and can do 200kph no problem. The 318i has exactly the same motor but different cam shaft and intake valve.
If u delete DISA, you loose the low end torque. You could have just bought a spare one from junkyard. Most of them work, because usually it's either cracked vacuum lines or one-way vacuum valve is shot. When DISA is working properly, it can definitely be felt.
its a great car for the price, and for long distance the 4 cylinder is a good choice. I have one too. If you want to drive more comfortable check out the E39 or the E46.