installed replacement fuel pump...but
 

there is a problem. when the car gets to operating temperature, the engine "pulses", it loses power and it sounds like it's missing. but it runs fine when it's cold. i have given up trying to find out what the problem is.


would going from an upgraded fuel pump to a stock flowing one cause the engine to lose power and "pulse" from power loss to full power very rapidly? i've given up.

Not a fuel pump problem.
This has to do with your engine control and all it's little sensors when it goes into closed loop operation at operating temperatures. A fuel pump is either on or off, working or not. Get your car to a scanner and someone that knows how to use it.

I asked you this before but did you get the correct fuel pump? Because the 98 cars use returnless fuel systems just like the 99+. Though I want to say its not 100% of the 98 cars are returnless.

Could be your O2 sensors went w/ the fuel pump. Are you throwing any codes for them?

no codes at all. still. :|