Upgrading Zip -> Ramfast bug?

[eddy@cs.ucdavis.edu (arekusu)]

In the continuing struggle to push my GS to 14+ MHz, I bought a
range of TTL crystals to experiment with. First, here's my setup:

Apple IIgs ROM3 (original w/ fixed ROMs)
AE Conserver (+ additional side fan)

1: (Hayes 14.4k faxmodem)
2: Grappler+ (HPDJ 550C)
3: (AppleColor RGB <- Super Famicom)
4: Zip GSX 10/64 v 1.02
5: Quickie (AEHD 3.5")
6: AE Audio Animator (AIWA NSX-5200)
7: RamFAST RevC 3.01e (Quantum 80Pro, Fujitsu 40)
M: OctoRam w/ 4 megs

After a large number of combinations, I found that the fastest
my GS will go is 10 MHz, using the 14 MHz CPU and the original
7400/7402. Using the faster 7402 in any combination kills the system
at power-on (by this I mean the cpu freaks out, sometimes it will
start clearing the screen from inverted @'s, sometimes nothing), the 
faster 7400 gives mixed results. Any crystal faster than 40 MHz (ie
clock speed of 12, 13.75, 15, 16) also kills the system, which makes
me think my CPU may be defective. 

So, the weirdness:

System powers up (into P8) and runs games etc just fine at 10 MHz.
Booting into the Finder either crashes during the thermometer or
freezes when the desktop appears, searching for drives. I have two
Prodos partions and one HFS partition. After many hours of frustration,
I found the ONLY way I can boot up correctly and have all partitions
available is to have the RamFAST driver and an >>OLD<< version
(modified 1990ish, so 5.0.4? unsure) of SCSI.Manager in the Drivers
folder. The 6.0.1 version, as well as no drivers, or any other
combination results in either a crash or no HFS partition.

I noticed the crash is always in driver code in bank 2, presumably
the RamFAST driver, since about 200 bytes before is a sequence of 
CVTECH strings.

So, could this be a problem with the driver itself and faster
CPU speeds? I have slot seven set to Fast, DMA on, CPS Follow on.
This setup worked fine before. Could it be voltage problems or a
weak power supply? I have not yet tried removing everything but
the Zip, since a stripped system is useless to me. I need it to
work just as is.

Has anyone else experienced these problems with fast Zips/RamFASTs?

thanks for all comments,

arekusu