Looooooooong list. Vacuum leaks, fuel pressure, TPS, Air Mass device, Fuel filter, Spark plug(s), Coil Packs; CPS; Throttle Body settings; VANOS problems; What Codes are being displayed/stored?; Blocked exhaust; Blocked Air Filter; Fuel pump; Loose wires on the EMC loom - That should do as a start
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 White and 1 Light Blue); E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i