Microsquirt Tuning? B16 Engine limps after 10 miles @ 75mph

[Mee]

Been researching the manual and have become quite intimidated trying to figure this out. I recenty acquired an Austin Mini with a Honday B16 Motor swap running DIS and Microspquirt. Previous owner claimed everything was running perfect and no problems such with the setup in his ten years ownership.

I drive the car home the first night and each ten or so miles running about 75-80mph the car goes into what might be described as limp mode, fuel begins to bog out, until you pull car off the side of the road, and come to a complete stop (engine still running). Then you can haul bum again for another 10 or so miles. Whatever fault causes resets when you pull over and complete to a complete stop for a second.

A few points of clarification;

Running DIS, (no dizzy)
Innovative Motorsports O2 sensor wired into Microquirt box.
Car runs, starts and shuts off, driveability is completely tip top around town! Getting half decent gas mileage too.
Problem like I said only happens if you run turnpike speeds, you will be buzzing along and then suddenly engine note changes, car loses power, (like its being electronically limited and will keep doing it until you stop) (if you stay under 60 it doesn't seem to happen)
Using 93 octane always
Car was set-up in the UK, car is now in the USA (philadelphia 300 feet above sea level)
I have logged about 700 miles in all sorts of conditions around town and no problems at ALL!
I have checked plugs, gapped and clean and in excellent condition
I have added fuel system cleaner and no change
Oil has been analyzed by blackstone and no reports of fuel leakdown (thought maybe I had a leaky injector or something)
Perhaps unrelated, but worth mentioning, car is running on tiny undersized 20" tall tyres and a 4.4 final drive in trans, so 5th gear going 75mph the engine isn't exactly silent, she's screaming...how many rpm you wonder? I don't know---no tach installed yet????

I'm mechanical, but when it comes to DIY EFI tuning and engine management, I'm on unfamilar ground.

I have no clue where to start, although I am going to try to data log this with the tuner studio software or whatever I was supposed to use the manual I've been reading about using the microsquirt

[Matt Cramer]

Are you able to capture this problem in a data log? If so, please post the log file along with your MSQ (tune) file. This will give us more to go on.

[Mee]

Are you able to capture this problem in a data log? If so, please post the log file along with your MSQ (tune) file. This will give us more to go on.

I'm new but I think I have all the downloads now to do this to connect later this evening. I dowloaded Tuner Studio MS, Megalogviewer, Megasquirt manual and sqlnet.log (innovate motorsports software for the O2 sensor).

I haven't been able to find diagnostics in any of this software yet thou.

Silly question, I imagine I have to get the car to go produce this result again correct. This could be a long file if it only happens every 10 miles of steady 75-80 mph....

[nakedninja900]

I had the exact same symptoms on a couple of toyotas years ago and it turned ou to be the fuel pumps, I think they got hot when cruising an having to continually supply high pressure ,when you pull over they cool down again etc etc.