Microstar dr8a, restricted in some way?

hmmmm, was quite happy to see this happen and wanted to know if there is some kind of restriction on it of some kind. You see what happened was ive mostly just used Ritek G04s and my supplier closed down so i went looking for another cheap suppliers and couldnt find any that i thought were reasonable. Then i found one that sold G05s so i tryed them out. As most of you know that they are 8x, and G04s are 4x. Well my burner
(http://www.msi.com.tw/program/products/optical_devices/dvs/pro_dvs_detail.php?UID=526)
burns dvd-r @ 4x and dvd+r @ 8x. But when i was burning with DVD Decrytper after about 20% writing it jumps from 4x up to 8x but only for about 25% and then drops down. Here is the log from DVD Decrypter:
I 15:17:28 DVD Decrypter Version 3.5.1.0 started!
I 15:17:28 Microsoft Windows XP Professional (5.1, Build 2600 : Service Pack 2)
I 15:17:28 Initialising SPTI...
I 15:17:28 Searching for SCSI / ATAPI devices...
I 15:17:28 Found 1 CD-RW, 1 DVD-ROM and 1 DVD±RW!
I 15:18:02 Operation Started!
I 15:18:02 Source File: D:\Images\Hi Octane Overboost.MDS
I 15:18:02 Source File Sectors: 2,285,838 (MODE1/2048)
I 15:18:02 Source File Size: 4,681,396,224 bytes
I 15:18:02 Destination Device: [1:0:0] ATAPI DVD RW 8XMax 150D (E (ATA)
I 15:18:02 Destination Media Type: DVD-R (Disc ID: RITEKG05) (Speeds: 2x, 4x, 8x)
I 15:18:02 Destination Media Sectors: 2,297,888
I 15:18:02 Write Mode: DVD
I 15:18:02 Write Speed: 8x
I 15:18:02 Test Mode: No
I 15:18:02 BURN-Proof: Enabled
I 15:18:02 Filling Buffer...
I 15:18:03 Writing LeadIn...
I 15:18:39 Writing Image...
I 15:29:57 Synchronising Cache...
I 15:30:15 Operation Successfully Completed! - Duration: 00:12:13
I 15:30:15 Average Write Rate: 6,752 KB/s (4.9x) - Maximum Write Rate: 11,151 KB/s (8.1x)

Just wantin to know if anyone knows how to burn @ a constant 8x with this drive. :-D Because this would be great, thanks

Edit. Just tryed burning a ISO Image with Nero 6 and it burns at a constant 8x. Im confused?