I replaced the original circa 1986 rubber gas lines in the engine compartment of my 1987 924S with the Rennbay kit. (The car ran fine but there were bubbles in the rubber hoses.) It was a tight fit working behind the Power brake drum, but I was able to cut the original lines with the provided pipe cutter and bolt the new lines with the compression fittings using 3/8" socket extensions and a 17mm crows foot dropped behind the brake drum and a 17 mm next to the oil dipstick, which I took out to make room for the operation. This process took me working on a Monday, Wednesday and Friday about 2 hours per session or aprox. 6 hours. I'm a slow worker because I think too much, look too much and try and understand everything about German engineering and how the car works etc.
When the new lines were in place I started the car like the instructions said and shut it off to check for leaks.

There was no leaks, however a new problem. I wasn't able to get the RPMs above 4,000 without it cutting out. Then it dropped down until I feathered the throttle and got it back to above a thousand, then 2 then 3 and at 4 it konks out again. So I was theorizing a couple things that I did during the fuel line change that might have affected the performance. 1.) I did pinch the fuel line with a clamp in the back out of the tank to the fuel pump, after a week of being pinched I let it loose and it didn't immediately come back to original shape, so I thought maybe the hose is still constricted inside cutting off the fuel supply which is the cause of the engine cutting off when the RPMs go up... Makes sense, but I'm not sure. It's a cheap $20 hose so I plan on replacing it. 2.) My second theory is that something broke loose inside the rear tank to fuel pump hose (like old fuel sludge, the car sat in a garage for a year before I got it) and got into the fuel filter causing it to clog and that's the problem. 3.) My only other guess is that some vacuum hose is off or leaking and that's affecting the performance.

Any suggestions or ideas? I don't have a fuel pressure gauge YET, but I see I will need one to further troubleshoot this issue.

Thanks for any help.