I don't know how the 328i behaves with only the manifold, ie how notisable that dip is.
My 128i 6mt + Disa only is very lively and satisfied my need for a tune & future proofed the car for me should I need the tune.
Cost was only ~300 + 6 hours of effort to install and time to clean used manifold.
128i Sport 6MT converted to Euro 130i spec, tuned by EVOLVE
In-progress: Evolve tune configuration!!; custom lip, some susp.
"The 1-series is the last car that BMW engineered before the Germans, as a car-making culture, fell out of love with driving." - R&T 2013 135is Review