The handheld vacuum pump is perfect for that, especially if it has a gauge. Poor or cheap injectors can drive you nuts with inconsistent mixtures.

You don't need a tee connector, actually it won't work with a Tee, just pull the hose off, plug the boot side and put the vacuum pump on the hose.

You shouldn't need a new fuel pump seal either.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)