The bristlecone pine "adjustment" for CO2 fertilization in MBH99, while genuflecting to Graybill and Idso , is completely different as seen in Figure 1 below.
Figure 1. Bristlecone pine CO2 adjustments. black solid – Graybill and Idso strup-bark; red dashed – MBH99
Graybill and Idso  hypothesized that tree ring "chronologies" for strip-bark forms would respond to higher CO2 concentrations in proportion to the total biomass response (benchmarked on their sour orange experiments), while "chronologies" for entire-bark forms would respond in proportion to trunk cross-sectional area (also benchmarked on sour orange experiments). Their Figure 4 shows the difference between strip-bark and entire-bark chronologies at Sheep Mountain and associates these differences with the above factors.
In order to detect this hypothesized response, strip-bark trees "were the primary focus of investigation wherever possible" in Graybill and Idso. (see page 86). In MBH99, a non-climatic effect on bristlecone pines was noted and an adjustment proposed for the 1000-1399 period. As I mentioned before, there is no adjustment in any results after 1400 in either MBH98 or MBH99. In passing, the existence of a non-climatic factor is contrary to one of the major assumptions of MBH98 and presumably should have occasioned a corrigendum to MBH98 at that time.
The adjustment developed in MBH99 bears no relationship to the Graybill and Idso analysis, as shown in Figure 1 below, where the two versions are compared. Graybill and Idso associate rising CO2 levels of the 20th century with enhanced ring widths; MBH99 argues that rising CO2 levels in the 19th century led to increased growth, but that the effect became saturated in the 20th century. I’m looking at MBH99 in more detail right now and will post up some details on how the MBH99 adjustment works (or doesn’t work). Since the MBH99 is so different from the Graybill and Idso  effect, it seems to me like there should have been some contemporary discussion as to the pros and cons of the MBH99 adjustment. It’s easy to see that the Graybill-Idso adjustment completely eliminates the hockey stick pattern from the bristlecone pines.
In passing, Graybill and Idso pointed out that two bristlecone chronologies lacked the growth increase after the mid-19th century (San Francisco Peaks AZ and Mount Goliath).