This is a very sad tale. If you have the old spring, what is the size ... wire diameter, coil number, spring id and, if possible, length. This may give you an idea of how well the new spring(s) match. Titan springs nearly always need shortening from new but if supplied in a kit I would expect them to have been sized already (I say this never having bought a kit). HW spring guides are not always a good fit. I do not know the original one used in a 99 ... new type with nylon (?) tube and a steel end? With an original HW mainspring I would expect some preload with maybe max of 25mm from end of cylinder to outer face of guide? But I say this from ignorance as I have never fettled a 99. If there is a lot more then I would suspect the wrong spring ... a check with dimensions of the old one could help here.
Whatever ... good luck, persevere and you will succeed.
Cheers, Phil