I've gotten Neal's opinion on the +4T vs. the +4BTT and he's pretty much convinced me to go the BTT route. To cement that decision I'd like to hear from anyone who has experience with both engines. If you could comment on the following differences in:

• Performance
• Maintenance
• Tunability
• Longevity

I know the differences may be minimal but I'm trying to justify the extra cost. Unfortunately cost is an issue because I'll be buying two engine/pipe combos and fuel from Neal at the same time...