1991 VW Jetta 1.8

Hi I was wondering if someone could could clarify the difference between the 2 1.8 litre engines. one is listed as 100 hp and the other is 105 hp. what gains the extra 5 hp and can I simply upgrade to get it.  also, what upgrades have the most bang for the buck?  I know there are turbo's and superchargers but they are pricey and I'm not sure how wise on a motor with 94,000 miles on it.  I know Intake and exhaust are usually the first step but does one give more gain than the other?  The car needs struts something awful, is it worth getting one of those lowering kits or just replace with stock parts?  I'm new to VW's any insight would be appreciated.


                  Mike