Last time you saw our Lightning McBarra MX-5 on your screens, Scotty had finished the long-awaited turbo upgrade as we get this thing ready to head to the drag strip.

The car formerly known as MX5.7 (due to the twin turbo LS1 swap we first did with it) has been rocking a Barra swap for just over two years now, debuting at Street Machine Summernats 33 with the new Ford heart and the Disney-inspired livery.

When we initially did that swap, we recycled one of the GCG turbos from the previous twin turbo LS setup to feed the Barra. It did the job just fine, but in the pursuit of power we soon found it was too small for the big 4.0-litre Ford mill.

So the crew from Pulsar turbos sorted us out with one of their bolt on GT3584R turbos to help us cram some more boost into the green top.

After getting distracted by our array of other Carnage project cars, the turbo finally found its way onto the MX-5. So this episode saw us head down to the dyno at Maxx Performance, where Barra tuning specialist Zane Heath to gave it a tickle to see if we could crack the 400rwkW barrier.

When the MX-5 was last on the dyno some 18 months ago, it made a best of 387rkW with the old turbo well and truly maxed out, so our hopes were high for a solid number with the bigger hairdryer.

Unfortunately, it wasn’t long until an incurable problem reared its head. Due to the LS and Barra conversions this car has endured, the wiring in it is a bit of a pizza. It’s given us dramas before, and this time around it was giving Zane headaches with the electronic boost control.

The car made a solid 301rwkW (404hp) on just 10psi, but that’s as far as we could go. The electronic boost control issues meant we couldn’t surpass that 10psi limit, so now a re-wire of the entire car is on the cards to get it up to scratch.