I searched and didn't come up with a vendor review for 555 Motorsports so I decided to post my own experience so far.
Just a brief background story. I had an upcoming turbo upgrade project and needed to track down a base map to support all the new mods. Mods included turbo, injectors, SSAC TMIC, GM BCS, and Tial EWG (plus the existing TBE and a couple other things). Initially I was going to go with a map from a well known internet tuner, but found out that I wasn't going to be able to. So I searched around and came across 555 Motorsports.
I emailed 555 Motorsports to explain the situation and heard back the next day from Mathew. This was a few weeks before the install day. Mathew was EXTREMELY helpful even with the first couple emails, and explained the details of what he does as far as internet tuning. I told him that I wanted to wait to pay (and didn't need the map yet) because the project wasn't ready. He was very understanding, and didn't hesitate to help answer questions I had, not only of the tune but of the project in general.
Fast forward to last week. I contacted Mathew again and told him I was ready for the map, and needed it by Saturday if at all possible. Again, his response was very prompt. I sent payment on (I believe) Wednesday night. Mathew responded late Wednesday night, like around midnight or so. A couple emails were exchanged regarding questions and whatnot, and by 11am the next morning I had my base map. I know Mathew was working on it until LATE Thursday morning, which completely impressed me.
Another fast forward. I loaded the map after the project last night. I haven't yet datalogged anything quite yet to send in for revisions, but I can say that the base map has made my car run smooth and strong...love it! I'm really looking forward to having Mathew tweak it here and there to see what we can get out of the car.
A HUGE thank you thus far in the tune process to Mathew. Very helpful and knowledgeable!