Sounds like your getting alittle better than average speed compared to the rest.90 on a good day is the highest I have ever heard on 500efi stock w/ full cabin!!.My factory test report from Hustler said 86.7mph.with bravos and stock 30s. Now with Bmax kinda messed up set up,the best I ever saw was 84 when I first bought it, after that it was 79 on a full,bad day and 82 on a good day.
I started out with 760 hp with the blower at 7 1/4 boost, a bad day full was 97-98 a good day lite was 99.
Thats a 1.30 gear 28 p 4 bl,at 6000rpm
Now I am at 840-860hp is running 100 with a little work ,in the cool it will hit 100 easy,but anything past that your catching a good day on the water, it likes a little chop .the best so far good water light and cool water 102.1gps.
Thats a 1.30 gear stock 30p props at 59-6000rpm. They may be a little more with tweaking the foots and props,maybe turning props in etc, I did buy a set of 32 I will try the when it gets cooler .our summer here has been 96-102temp, water is 92 humidity is above 60 all the time.I would say adding power past say 780hp you starting to hit a wall around 97-99mph.
The most hp Ive seen out of a na 500efi taken all the way was 648hp from 2 diff builders and that was pushing it!! its about 15k each, its cheaper to put on the Whipple and turn it down to put ya at low 700hp.Thats what I would do!! Depends on how ya drive it on the drive ,Remember the Whipple builds boost real quick , mine was from 3500 to 4600 above 850TQ at the 860 hp setting.Ya dont stab it around there very often with a bravo
With the bigger pulley it was at 7.11lbs, 808tq at 4100 and 779 at 6000.
I think I have a dyno sheet from the first time with the Whipple with a 5 or 4.75 pulley which should be in the low 700hp range??
Your 388 should be a lot of fun in the low 700hp and be reliable and handle good .