Long time lotus esprit owner here. Then I bought a Porsche C4S (naturally aspirated). But the C4S would not compare to your GT4 (turbo, I assume). My C4S seemed as quick as anything taking off, solid vehicle.
I traded the C4S for my MP4 (get use to saying 12C rather than MP4 ... everybody just drifted to '12C')
Just so different. Aesthetically, in the Porsche, people would say "nice car". In the 12C, magnify that by 100 X ! Mobs of people everywhere you will stop, pics, etc.
I like to cruise in the 12C at 105 mph @ 3000 rpm's -- reminds me how much more there is. I drove my Lotus to 170 mph, Porsche to 165 and 12C to 190 mph. The mid-engine cars seemed better handling.
Hopefully, a McLaren owner who has tracked a Porsche GT4 can help you here. Good luck!