Normally aspirated engines are notoriously difficult to get gains from simply with a remap.
The rear quad exhausts should give you a mild gain over the restrictive stock exhausts; however, unless you get into expensive internal engine modifications, I am less inclined to believe you'll see vast gains from a simple NA remap.
I'd be very interested to see bhp gains on an RTCC remap proven with a before and after dyno run. I'd also be interested to hear who's remap it actually is (who created the map), if it is simply a map done by someone like DMS for the engine when it is housed in a BMW, again I'd question the benefit.
Phil, as a start, have you had the car on a rolling road? You'll soon see how close to stock quoted figures you are. If you are close, I'd be tempted to revert to stock for all the reasons you mention. You certainly aren't the first person to mention the ammonia smell post remap.
