After putting the new 5 series pump in, so much fuel was coming into the fuel filter in front of the Kugelfisher that it was probably dragging some old, dead rubber and other crud in the fuel lines into the filter.

The end result was serious starvation at times about 4000 RPM. The car would run great until enough pressure was being generated into the fuel filter that with the junk in it, there was restriction.

We took a hacksaw to the fuel filter and on the inside of the new (about 4 months ago) stock filter, it was so black you couldn't make out what color the original filter material was.

Bottom line is that the filter is about 3 times the size and flow of the stock filter, and is about 2 times the money ($20) and are readily available from parts houses. The only downside was I didn't have a large enough hose clamp to hold it to the firewall so it's on there temporarily with a couple of cable ties. I can now easily find 5500-6000 rpm and no hesitation at all. I also believe that there is an added benefit to having about 16 oz of filtered fuel available at at time rather than a 8 ounces which is about the capacity of the old unit.