I have to say that I have some problems with this (revised) paper. The topic sounds interesting and the paper is well written albeit somewhat overly detailed. The title talks about "Improving Air Quality predictions using...". The first sentence of the abstract suggests the same, assessing the impact of revised VOC and OA emissions estimates .... on air quality predictions for...". Most readers would then expect like me to find a paper reporting improved air quality predictions but that is not what we get. Instead, you merely report how the use of top down emission estimates better constrains the fugitive emissions in the OS region. That is a much more restricted objective, I would expect to read how air quality predictions on things like oxidants (ozone) and particles in the air were improved by using those better constrained emission data. The actual results reported in the paper are extensively discussed which may of interest and merit publication, but then say so up front.
The paper is also overly long, as mentioned by referee 1 (who also made some comments about the original title). You mention that you shortened the paper upon referee 1's comments. Well that sounded odd to me so I counted: the original paper had an abstract of 34 lines, 7 lines shorter that the revised version. The original main text runs from lines 50-603, the revised version runs from lines 43-628... So I feel there is work to do.
One of the things that makes the paper so long is the amount of detail. I do not know the Zhang et al. paper, now accepted for ACP, but I suspect that there is quite some overlap with section 2.1, so reference to that paper should be possible. Similarly section 2.3 may well include a lot of the details already reported in the Li et al. and Liggio and al. papers, so again, references to those papers should be possible. In short, only describe what is new and refer for the rest to those earlier papers. One further comment: lines 169-171 mention that the PM2.5 emissions in Table 1 are derived only for the summer months which seems eminently sensible. But it makes me wonder whether the same should be true for the gaseous VOCs. Are there wintertime aircraft observations for these VOCs suggesting that fugitive emissions are more or less the same?
I do not want to say much on chapter 3, the revised version after the referee comments seems fine to me. Allow me to make a few comments and suggestions:
* a lot of space is used for detailed case studies. I am wondering whether it would not make sense to move most of the case studies to the supplement (lines 207-338, figures 2-3; lines 359-386, figures 6-8; lines 403-444, figure 10; lines 486-543, figures 14-16), and only write a few paragraphs in the main body of the text summarizing these case studies
* chapter 4, Discussion, only pertains to the results in chapter 3.4. Therefore make current chapter 3.4 into 3.4.1, and chapter 4 into chapter 3.4.2.
Finally, among the conclusions (should now be Chapter 4!) I note your comment on the especially large increases in the ALKA compounds at the facilities that use paraffins for bitumen extraction. That seem to me like an important observation that should also be mentioned earlier (in chapter 2).
I do apologize for giving you my comments and assessments rather late. Part of the reason for this was that I was waiting for your responses to the referee comments which I expected to take care of most of what I had to say. However with some dedicated effort it should not take too much effort to implement all of the above, especially concerning a better descriptive title and shortening the paper. To be sure I will give you more time than I expect will be necessary, hence the rating reconsider after major revisions.
Jan Bottenheim

Manuscript accepted for publication in ACP. There are a few minor issues you should clean up before sending your final manuscript (hence "publish subject to technical corrections"):
(1) I am not sure whether you have defined all your acronyms/abbreviations at the first (or only) time they show up in the text, for instance ADOM, GEM (different from GEM-MACH), EPA (every reader should know this one of course but hey, you also define ECCC). Also I believe OA is defined twice.
(2) line 371: should be chapter 3.4.1, not 3.4, while line 406 chapter 3.4.2 should be bold. Line 464 should be titled 4. Conclusions (number is missing).
(3) as an afterthought: while you now correctly state that you are concerned with the question how the top down data for emission profiles improves the predictions of the organic species better, what we really would like to know is how these improved data modify (if at all) the air quality predictions. After all, the first sentence in the introduction indicates that this what the whole project is about. Would have been nice if you could have made some comments on this.
In any case, congratulations with a nice paper. Jan Bottenheim