im not sure how this setup is supposed to be on a 98 rs, He has a lack of power and lean spot after about 4grand, i saw in all the hookups the FMU is supposed to be run with a stock press regulator but whoever did this kids setup is running only an fmu on the return line. no stock reg at all. i assume this is causing the problem , can this cause it? oem injectors, 12:1 fmu. 6 psi .

Welcome to 2gnt. Learn to type better, because you’re not making any sense.

“He” needs to have the stock fpr in conjunction with the fmu. Period. The stock fpr takes control of the fuel pressure when the engine isn’t under boost. As for why “he’s” running lean can be a number of things, first thing the ditto needs to do is hook up his stock fpr. 12:1 fmu with stock injectors sounds right, make sure “he” doesn’t have the fmu installed backwards

Last but not least SEARCH, this will answer 99.9% of your common turbo answers

You might have an SFMU and your confusing the two.

Is this what you have: