I have a 95 1.6 16 valve that is running rich and getting terrible milage. is it the ECU,Mapp sensor or what?
also is there an after market chip/ computor that is actually worth installing
thanks for your help.

02 sensor is a good bet to start things off.  If that has gone bad then it will throw all of your mappings off.

16V engines have a MAF, make sure it's clean, but don't stick anything in there to
try and clean it, just get a can of MAF spray cleaner and check/change your air filter
while you are at it.

x2 on the O2 sensor, or at least check it's operation and if it's sending the signal

Wild

All the " chips" are bogus.

No they aren't, Ruffles and Frito's are both excellent with dip 

LOL

  Yeah, and sunchips too!

Is your CEL on?  That can also point you in the right direction.  I don't remember if the 16v for 95 is OBDII, but if it is, that'll help you out too.  Usually a dirty MAF doesn't make it run rich, but lean.  This is due to the fact that the dirty sensor can't accurately read the air coming in-it thinks it's getting less air (dirt/debris insulates the heating element) so won't give it as much fuel.  Air filter would be a good place to start.  Also check your coolant temp sensor.  If your computer is seeing the engine isn't warmed up when it actually is, it could be giving more fuel than necessary.  Hope this helps!

95 is the ODBI setup, the only year of the 2 doors with the 16 vavle engine before they went ODBII based in 96.