PROBLEM WITH MIDI ON NEW IMAC

Just gone from pc to a imac, set up worked on pc but now with imac i have a delay of 2or3 secs on plug ins sound from hitting keyboard to hearing sound, audio works fine. Have updated driver for m=audio 4x4 midisport midi hardware with no joy, have midi light when hitting keys instantly and vu in mixer in cubase6 but vu on output shows after delay and sound is heard is it cubase midi hardware or new computor.
i am running a 27inch imac 10.6.8 cubase6 with plug ins [omnisphere halion4 rmx etc] steinbergMR816csx m=audio4x4 midisport and master keyboard korg Oasys.
Any help would be much appreciated .

Sounds like you don’t have the correct ASIO driver selected.

Also, it could be that your ASIO buffer is set to something unnecessarily high.
Have you checked the buffer size?
Sincerely,
J.L.

ASIO DRIVER OK AUDIO WORKS OK ITS THE MIDI THATS NOT WORKING CORRECTLY HAVE CHECKED SETTINGS IN MAC AUDIO\MIDI SET UP EVERY THING SEEMS FINE BUT STILL GOT DELAY ON PLUG IN SOUNDS

Have you tried it on a blank project with no plugins VST instruments etc apart from the one?

My iMac sometimes develops this issue when the track becomes loaded with multiple VSTi’s and plugins. At this point I bounce things down to audio.