Nginx 502 Bad Gateway - 111: Connection refused, port not being listened to

I'm aware there are many other similar questions but the solutions from those questions I feel I've already got in place.

I've got 3 sites running locally on a VirtualBox Ubuntu 12.04.4 LTS Server, I'm using nginx and php-fpm.

They are configured to run on ports 9001 -> 9003:

server:/etc/php5/fpm/pool.d$ grep 900 *
my-app-deploy.conf:listen = 127.0.0.1:9002
my-app-dev.conf:listen = 127.0.0.1:9001
my-web.conf:listen = 127.0.0.1:9003

server:/etc/nginx/conf.d$ grep 900 *
my-app-deploy.conf:                fastcgi_pass   127.0.0.1:9002;
my-app-dev.conf:                fastcgi_pass   127.0.0.1:9001;
my-app-web.conf:                fastcgi_pass   127.0.0.1:9003;

I've restarted both php-fpm and nginx successfully:

server:$ sudo service nginx restart
 * Restarting nginx nginx
   ...done.
server:$ sudo service php5-fpm restart
 * Restarting PHP5 FastCGI Process Manager php5-fpm
   ...done.

But if I look at what ports are being listened to, I only see 9002 and 9003:

server:$ sudo lsof -i | grep 900
php5-fpm  1020     root    7u  IPv4   8557      0t0  TCP localhost:9002 (LISTEN)
php5-fpm  1020     root    8u  IPv4   8558      0t0  TCP localhost:9003 (LISTEN)
php5-fpm  1021 www-data    0u  IPv4   8557      0t0  TCP localhost:9002 (LISTEN)
php5-fpm  1022 www-data    0u  IPv4   8557      0t0  TCP localhost:9002 (LISTEN)
php5-fpm  1023 www-data    0u  IPv4   8557      0t0  TCP localhost:9002 (LISTEN)
php5-fpm  1024 www-data    0u  IPv4   8557      0t0  TCP localhost:9002 (LISTEN)
php5-fpm  1025 www-data    0u  IPv4   8558      0t0  TCP localhost:9003 (LISTEN)
php5-fpm  1026 www-data    0u  IPv4   8558      0t0  TCP localhost:9003 (LISTEN)
php5-fpm  1027 www-data    0u  IPv4   8558      0t0  TCP localhost:9003 (LISTEN)
php5-fpm  1028 www-data    0u  IPv4   8558      0t0  TCP localhost:9003 (LISTEN)

And I get the following error from nginx:

server:~/vhosts/my-app/logs$ tail -n 1 nginx/error.log 
2014/06/20 11:07:36 [error] 2434#0: *4 connect() failed 
    (111: Connection refused) while connecting to upstream, client: 192.168.0.10,
    server: my.app.dev, request: "GET /api/test.php HTTP/1.1", upstream:
    "fastcgi://127.0.0.1:9001", host: "my.app.dev"

I'm hoping I've just missed something really basic, but when I added the site on 9002 I don't remember having to do anything else apart from add the new port number to both the conf files

UPDATE The site root is actually serving, it's only the api/test.php page that is returning 502

UPDATE I moved the ports around, I swapped web and dev around so dev is now on the 9001 port, but that's made no difference. I've updated the question to reflect this.

All 3 ports are serving content - I think it's something to do with redirects I've got setup for the API section.

Here is a diff between the dev and deploy PHP and nginx configs:

server:/etc/nginx/conf.d$ diff my-app-dev.conf my-app-deploy.conf 
3c3
<         server_name my.app.dev;
---
>         server_name my.app.deploy;
10c10
<         root /var/www/vhosts/my-app/public_html/mobile;
---
>         root /var/www/vhosts/my-app/public_html/mobile_deploy;
47c47
<                 fastcgi_pass   127.0.0.1:9001;
---
>                 fastcgi_pass   127.0.0.1:9002;

server:/etc/php5/fpm/pool.d$ diff my-app-dev.conf my-app-deploy.conf
33c33
< listen = 127.0.0.1:9001
---
> listen = 127.0.0.1:9002
384c384
< php_admin_value[doc_root] = /var/www/vhosts/my-app/public_html/mobile
---
> php_admin_value[doc_root] = /var/www/vhosts/my-app/public_html/mobile_deploy

And here is the complete conf file for the dev site, on port 9001, that is giving me the 502

server {
        listen 80;
        server_name my.app.dev;

        error_log  /var/www/vhosts/logs/my-app/nginx/error.log;
        access_log /var/www/vhosts/logs/my-app/nginx/access.log  main;

        error_page 404 /404;

        root /var/www/vhosts/my-app/public_html/mobile;
        index index.html index.php;

        client_max_body_size 10M;

        proxy_read_timeout 180s;

        # deny any attempt to access hidden files
        location ~ /\. { deny all; }

        # disable logging for favicon
        location = /favicon.ico {
                log_not_found off;
        }

        location ~* \/api\/[0-9]\/.*\.zip {
                try_files $uri /api/3/nomarket.data.zip;
        }

        location ~* \/api\/picture\/[a-z]+\/? {
                if (!-e $request_filename) {
                        rewrite ^/api/picture/([a-z]+)/? /api/picture.php?type=$1 last; break;
                }
        }

        location /api {
                if (!-e $request_filename) {
                        rewrite ^/api/(.*)$ /api/router.php?rest_data=$1 last; break;
                }
        }

         # allow php files to be executed
        location ~ \.php$ {
                # only call php if the file exists. Very important for security!
                try_files  $uri =404;
                include /etc/nginx/fastcgi_params;
                fastcgi_pass   127.0.0.1:9001;
                fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
                fastcgi_index  index.php;
        }

        # just serve static files, please.
        location / { }
}