ScoobyDoo555

OK. Really need the wealth of Scoobynet's expertise on this one.

MY99 UK, 82,000 miles. only mods are decat c.section and backbox (Scoobysport) been running fine up to last service.

Symptoms -

Lacks any urgency (almost holding back) through the revs.
Most noticeable from 3 - 4000 revs, where it starts to judder.
Havent' taken it any higher through fear!!!

No dodgy idling issues - MAF
No change in fuel consumption.
No error codes from ECU - doesn't rule out a failing MAF or Lambda, but:

Things that have been changed -

82.5K service a few weeks ago
To rectify problem, so far -

1. Brand new NGK spark plugs
2. New ignition pack

Trying "some new leads" (HT leads?) tomorrow

any ideas what else it may be, apart from the obvious (cleaning the boost solenoid - potential overfill of oil?)

Answers on a postcard

Dan