if u place 4G93 cam into your 91 head,actually not much different like last time i do...
then u will find out u need the full set completed head for better result..
then u will find the REV cut too early due 4G91 cut around 6.5k,but still feel that u can gain some more..
then change 4G93 ECU,
now REV can go to 8.5k...
u will find 4G91 cam power show up early and end early..
but the 4G93 cam can give u more power around 6k RPM...
now i using GSR intake,but really,if u maintain 4G91 head,better stay with your original intake...
if u choose 4G93 head,the best intake is the GSR intake for better quick response..
just my opinion....