The secret was that they weren't expecting the TWR-built VL to come out were they?
Mr Perkins had 2 VL batmobiles built and ready to run for 1988.. one became a T car.. and Mr Walkinshaw chose to run his own car.
There was an issue with revs in the Perkins engines.. Mr Small apparently sold parts to TWR for an engine program, maybe not the EFI version, but Holden V8 definitely. In 1986, Mr Grice managed to pull 8,000 rpm out of his Holden powerplant on the way to victory... so maybe Mr Walkinshaw expected that level of hunger from the Perkinsmobile...